Key Points

  • KIR B haplotype donors limit relapse after reduced intensity conditioning URD allotransplantation.

  • All donor KIR B genes contribute to relapse protection in recipients having C1+ HLA-C.

Abstract

Natural killer (NK) cell recognition and killing of target cells are enhanced when inhibitory killer immunoglobulin-like receptors (KIR) are unable to engage their cognate HLA class I ligands. The genes of the KIR locus are organized into either KIR B haplotypes, containing 1 or more activating KIR genes or KIR A haplotypes, which lack those genes. Analysis of unrelated donor (URD) hematopoietic cell transplants (HCT), given to acute myeloid leukemia (AML) patients between 1988 and 2009, showed that KIR B haplotype donors were associated with better outcomes, primarily from relapse protection. Most of these transplants involved marrow grafts, fully myeloablative (MAC) preparative regimens, and significant HLA mismatch. Because the practice of HCT continues to evolve, with increasing use of reduced intensity conditioning (RIC), peripheral blood stem cell grafts, and better HLA match, we evaluated the impact of URD KIR genotype on HCT outcome for AML in the modern era (2010-2016). This analysis combined data from a prospective trial testing URD selection based on KIR genotypes (n = 243) with that from a larger contemporaneous cohort of transplants (n = 2419). We found that KIR B haplotype donors conferred a significantly reduced risk of leukemia relapse and improved disease-free survival after RIC, but not MAC HCT. All genes defining KIR B haplotypes were associated with relapse protection, which was significant only in transplant recipients expressing the C1 epitope of HLA-C. In the context of current HCT practice using RIC, selection of KIR B donors could reduce relapse and improve overall outcome for AML patients receiving an allogeneic HCT.

Introduction

After allogeneic hematopoietic cell transplant (HCT), natural killer (NK) cells are the first population of lymphocytes to reconstitute. Consequently, they can affect the outcome by promoting engraftment, preventing acute graft-versus-host disease (GVHD), contributing to a robust immune reconstitution, as well as limiting the risk of leukemic relapse.1,2  NK cells secrete cytokines and mediate cell killing by direct natural cytotoxicity and through antibody-directed cellular cytotoxicity. Several families of activating and inhibitory NK cell receptors contribute to immunosurveillance by these innate immune system components, and the net signaling balance determines the NK cell response to damaged, virally infected, or malignant target cells. The highly polymorphic family of killer-cell immunoglobulin-like receptors (KIR), encoded on chromosome 19, has coevolved with the MHC class I family and has been well studied in the context of HCT.3,4  In humans, inhibitory KIR (3DL1, 2DL2/3, and 2DL1) recognize the Bw4, C1, or C2 epitopes of HLA class I, respectively. These inhibitory ligand-receptor interactions govern the education and functional maturation of NK cells through the mechanism of missing self-recognition.5,6  Mature NK cells mediate stronger effector functions when they encounter cells that have downregulated self HLA class I. This phenomenon is common to tumor cells and virally infected cells and is a mechanism that allows them to escape from T-cell recognition. Allogeneic HCT donors can have inhibitory KIR, for which the patient lacks the cognate ligand; during the patient’s reconstitution, these alloreactive NK cells can provide a strong antileukemia response. This effect was first demonstrated by Velardi and coworkers in Perugia, who showed that patients receiving haploidentical HCT for leukemia were protected from relapse when the donor:recipient pair were KIR ligand mismatched.7 

Subsequently, the importance of donor KIR gene haplotypes for the outcome of allogeneic transplants for acute myeloid leukemia (AML) was reported.8,9  The KIR A haplotype is defined by a fixed content of genes, encoding 6 inhibitory KIR (KIR3DL3, 2DL3, 2DL1, 2DL4, 3DL1, 3DL2) and 1 activating KIR (KIR2DS4). The KIR B haplotypes are characterized by the presence of 1 or more of the genes encoding 5 activating KIR (KIR2DS1, 2DS2, 2DS3, 2DS5, 3DS1) and 2 inhibitory KIR (2DL2, 2DL5). Previously, we showed that donors having KIR B haplotypes protect against relapse after myeloablative unrelated donor (URD) HCT for AML, but not for acute lymphocytic leukemia.8,9  This protection was seen in both HLA-matched and HLA-mismatched transplants, with the strongest relapse protection occurring when the donor is homozygous for centromeric (Cen) KIR B haplotypes. We also reported that patients homozygous for HLA-C2 epitopes have the worst outcome, whereas the benefit of a KIR B donor was most pronounced when patients carried HLA-C1.10  Other investigators11,12  have reported a particular benefit associated with KIR2DS1+ donors, especially in patients with HLA-C1. Here we analyze URD HCTs for AML that were all performed after 2010. This study included a cohort collected for a prospective trial of KIR donor selection (KIR DS)13  and a larger contemporaneous group.

Methods

For the prospective KIR DS trial (2012-2016)13  and the larger contemporaneous cohort (2012-2016), patient and donor demographics, transplant approach, and outcome data were collected through the Center for International Blood and Marrow Transplant Research (CIBMTR), using standard data collection processes and forms. Data were curated and error checked using CIBMTR procedures supplemented with the KIR genotyping data collected for the KIR DS prospective trial. KIR genotypes for the contemporaneous cohort of patients and donors (those patients and donors not in the prospective KIR DS trial) were collected retrospectively through the retrospective typing project of the National Marrow Donor Program (NMDP).14  Donor KIR genotypes were used to assign KIR AA vs B/x haplotypes as previously reported.8,9  Patients and donors provided consent for the data collection and subsequent analyses, with approval by participating institutions and the CIBMTR/NMDP institutional review board.

Using clinical and genotyping data from both our prospective KIR DS trial13  and the contemporaneous cohort from the NMDP and CIBMTR, we evaluated the demographic and donor KIR genotype influences on outcomes, including relapse incidence, nonrelapse mortality (NRM), disease-free survival (DFS), and overall survival (OS). Unadjusted outcomes between groups with differing donor KIR genotypes were analyzed with an indicator variable for transplants in the prospective KIR DS trial vs the larger, contemporaneous cohort. Median follow-up of survivors was 36 months in the prospective trial and 44 months for the large contemporaneous cohort.

Clinical and demographic variables were evaluated for their impact on outcome analyses tested in univariate and multivariate analyses. Cox proportional hazards models were used to adjust for significant clinical factors. The proportional hazards assumption was evaluated using a time-dependent covariate method, and factors with nonproportional hazards were adjusted through stratification. Forward stepwise regression modeling was performed to identify clinical and patient factors that influenced transplant outcome: considering patient age, disease status, donor-recipient gender, gender match of donor and recipient, HLA match of donor and recipient, status for the C1 and C2 epitopes of HLA-C for donor and recipient, graft source (either bone marrow or filgrastim-stimulated peripheral blood stem cells [PBSC]), conditioning of the patient (either myeloablative [MAC] or reduced intensity conditioning [RIC]), with the latter including nonmyeloablative (NMA); cytomegalovirus (CMV) serostatus of donor and recipient; pretransplant Karnofsky performance score; antithymocyte globulin (ATG)/alemtuzumab use; GVHD prophylaxis; the use, or not, of total body radiation; the time from diagnosis to HCT; HLA-DP permissive mismatch; and year of HCT. Donor KIR genotype variables were tested separately by forcing each into the multivariate models. Interactions between KIR genotype variables and the adjusted clinical factors were tested, and no significant interactions were detected. Cases (or factors) were excluded from some models if outcome data or significant covariates were missing. To adjust for the multiple testing, the significance threshold of 0.05 was used for the donor KIR haplotypes, 0.025 for donor centromeric regions, and 0.007 (0.05 divided by 7) for the donor KIR genes. All analyses were done using SAS, version 9.4.

Results

Comparison of URD transplants performed in 1988-2009 to those performed in 2010-2016

In previous retrospective analyses, we showed that donors having 1 or 2 KIR B haplotypes protect against relapse of AML after URD HCT.8,9  That study analyzed transplants performed before 2010 using myeloablative conditioning, predominantly marrow graft sources, and HLA- matching characteristics that were less stringent than currently used. Based on the observed advantage conferred by donors with KIR B haplotypes, we performed a multicenter prospective KIR DS trial between 2012 and 2016 to enrich for donors with favorable KIR haplotypes. In 535 searches, 2080 prospective donors were typed; 243 of these led to transplantation. The process for KIR donor selection and its capacity to enrich for favorable KIR haplotype donors has been published.13  However, there has been no recent analysis to assess the effect of donor KIR haplotypes in the modern transplant era. Acknowledging that the modest size of our prospective KIR DS trial prohibited adequately powered evaluation, we addressed this important question with an analysis that included a contemporaneous (2010-2016) CIBMTR retrospective cohort. The supplemental cohort included 2419 transplanted AML patients with available KIR genotyping of the donors, none of whom were included in the prospective trial.

The patients enrolled in the prospective KIR DS trial group have similar characteristics to those in the larger contemporaneous cohort. Both cohorts included subgroups receiving MAC and RIC/nonmyeloablative conditioning and within each cohort those 2 groups had comparable race, gender, gender match, donor/recipient CMV serostatus, and HLA matching (Table 1). Nearly 60% of all HCTs did not include either ATG or alemtuzumab, which are known to bind and deplete, at least partially, reconstituting NK cells.15  When comparing between conditioning regimens irrespective of cohort, a greater proportion of patients undergoing RIC received mobilized PBSC grafts, fewer had Karnofsky performance scores of 90% to 100% vs 10% to 80%, or comorbidity index scores of 0 to 3 vs 4+, and the median age was higher. Compared with the contemporaneous group, a smaller proportion of the KIR DS trial cohort were CMV seropositive, fewer had HLA < 8/8 allele-matched donors, and nearly one-half had HLA-DP permissive mismatches in both cohorts. The frequency of donor KIR genotypes (AA vs Bx), including the centromeric regions was similar in the 2 cohorts.

Figure 1.

Recipient C1x and donor KIR Bx improves relapse and DFS after RIC HCT. Recipient C1x (A) and C2C2 (B) relapse at 3 years. Recipient C1x (C) and C2C2 (D) DFS at 3 years.

Figure 1.

Recipient C1x and donor KIR Bx improves relapse and DFS after RIC HCT. Recipient C1x (A) and C2C2 (B) relapse at 3 years. Recipient C1x (C) and C2C2 (D) DFS at 3 years.

Table 1.

Demographics: contemporaneous and prospective KIR DS trial cohorts

Contemporaneous cohortProspective KIR DS trial
RIC/NMAMACRIC/NMAMAC
987 1432 96 147 
No. of centers 98 109 10 15 
Recipient age, y     
 Median (range) 64 (20-84) 49 (20-76) 65 (28-78) 51 (20-75) 
Recipient race/ethnicity     
 White, non-Hispanic 897 (93) 1250 (89) 93 (97) 139 (95) 
Recipient sex     
 Male 544 (55) 707 (49) 54 (56) 73 (50) 
 Female 443 (45) 725 (51) 42 (44) 74 (50) 
Karnofsky performance score     
 90-100 525 (53) 987 (69) 55 (57) 98 (67) 
 10-80 450 (46) 425 (30) 41 (43) 49 (33) 
HCTcomorbidity index scores     
 0 210 (21) 401 (28) 13 (14) 26 (18) 
 1-3 502 (51) 756 (53) 51 (59) 67 (46) 
 4+ 272 (28) 274 (19) 26 (27) 54 (37) 
Recipient CMV serostatus     
 Negative 335 (34) 460 (32) 39 (42) 61 (43) 
 Positive 645 (66) 962 (68) 53 (58) 81 (57) 
Donor:recipient HLA allele match 
 8/8 849 (86) 1196 (84) 88 (92) 135 (92) 
 7/8 138 (14) 236 (16) 8 (8) 11 (7) 
HLA DP matching     
 Fully matched 164 (17) 240 (17) 14 (18) 29 (23) 
 Permissive mismatch 481 (49) 687 (48) 43 (54) 55 (44) 
 Nonpermissive mismatch 340 (36) 501 (35) 23 (29) 40 (32) 
Recipient C1 allele present     
 Yes 866 (88) 1213 (85) 84 (88) 122 (83) 
Graft type     
 Marrow 79 (8) 274 (19) 11 (11) 33 (22) 
 PBSC 908 (92) 1158 (81) 85 (89) 114 (78) 
Donor age     
 Median (range), y 28 (18-61) 29 (18-61) 23 (23-23) 39 (27-50) 
Conditioning regimen groups     
 RIC/NMA: TBI ± other 177 (18)  29 (30)  
 RIC/NMA: Flu/Clof ± other 399 (40)  5 (5)  
 RIC/NMA: alkylator based 411 (42)  62 (65)  
 MAC: TBI ± Bu or Cy or other  269 (19)  20 (14) 
 MAC: non-TBI  1164 (81)  127 (86) 
ATG/alemtuzumab use     
 ATG + alemtuzumab 0 (0) 1 (< 1) 0 (0) 0 (0) 
 ATG alone 385 (39) 569 (40) 27 (28) 24 (16) 
 Alemtuzumab alone 39 (4) 25 (2) 4 (4) 7 (5) 
 No ATG or alemtuzumab 562 (57) 836 (58) 65 (68) 116 (79) 
Disease status at transplant     
 Early 777 (79) 1084 (76) 69 (72) 79 (54) 
 Intermediate 210 (21) 348 (24) 13 (14) 28 (19) 
 Advanced 0 (0) 0 (0) 14 (15) 40 (27) 
Cytogenetics     
 Good 35 (10) 108 (20) 6 (7) 10 (8) 
 Intermediate 255 (72) 331 (62) 63 (69) 92 (70) 
 Poor 64 (18) 97 (18) 22 (24) 29 (22) 
 Unknown, n 633 896 16 
Follow-up among survivors, mo    
 No. evaluated 440 759 48 74 
 Median (range) 38 (6-99) 46 (2-98) 36 (12-73) 36 (12-72) 
Donor KIR haplotype     
 AA 319 (32) 454 (32) 18 (22) 39 (29) 
 B/x 668 (68) 978 (68) 65 (78) 96 (71) 
Donor centromeric region score    
 AA 455 (46) 689 (48) 32 (39) 61 (45) 
 AB 442 (45) 594 (41) 43 (52) 58 (43) 
 BB 90 (9) 149 (10) 8 (10) 16 (12) 
Contemporaneous cohortProspective KIR DS trial
RIC/NMAMACRIC/NMAMAC
987 1432 96 147 
No. of centers 98 109 10 15 
Recipient age, y     
 Median (range) 64 (20-84) 49 (20-76) 65 (28-78) 51 (20-75) 
Recipient race/ethnicity     
 White, non-Hispanic 897 (93) 1250 (89) 93 (97) 139 (95) 
Recipient sex     
 Male 544 (55) 707 (49) 54 (56) 73 (50) 
 Female 443 (45) 725 (51) 42 (44) 74 (50) 
Karnofsky performance score     
 90-100 525 (53) 987 (69) 55 (57) 98 (67) 
 10-80 450 (46) 425 (30) 41 (43) 49 (33) 
HCTcomorbidity index scores     
 0 210 (21) 401 (28) 13 (14) 26 (18) 
 1-3 502 (51) 756 (53) 51 (59) 67 (46) 
 4+ 272 (28) 274 (19) 26 (27) 54 (37) 
Recipient CMV serostatus     
 Negative 335 (34) 460 (32) 39 (42) 61 (43) 
 Positive 645 (66) 962 (68) 53 (58) 81 (57) 
Donor:recipient HLA allele match 
 8/8 849 (86) 1196 (84) 88 (92) 135 (92) 
 7/8 138 (14) 236 (16) 8 (8) 11 (7) 
HLA DP matching     
 Fully matched 164 (17) 240 (17) 14 (18) 29 (23) 
 Permissive mismatch 481 (49) 687 (48) 43 (54) 55 (44) 
 Nonpermissive mismatch 340 (36) 501 (35) 23 (29) 40 (32) 
Recipient C1 allele present     
 Yes 866 (88) 1213 (85) 84 (88) 122 (83) 
Graft type     
 Marrow 79 (8) 274 (19) 11 (11) 33 (22) 
 PBSC 908 (92) 1158 (81) 85 (89) 114 (78) 
Donor age     
 Median (range), y 28 (18-61) 29 (18-61) 23 (23-23) 39 (27-50) 
Conditioning regimen groups     
 RIC/NMA: TBI ± other 177 (18)  29 (30)  
 RIC/NMA: Flu/Clof ± other 399 (40)  5 (5)  
 RIC/NMA: alkylator based 411 (42)  62 (65)  
 MAC: TBI ± Bu or Cy or other  269 (19)  20 (14) 
 MAC: non-TBI  1164 (81)  127 (86) 
ATG/alemtuzumab use     
 ATG + alemtuzumab 0 (0) 1 (< 1) 0 (0) 0 (0) 
 ATG alone 385 (39) 569 (40) 27 (28) 24 (16) 
 Alemtuzumab alone 39 (4) 25 (2) 4 (4) 7 (5) 
 No ATG or alemtuzumab 562 (57) 836 (58) 65 (68) 116 (79) 
Disease status at transplant     
 Early 777 (79) 1084 (76) 69 (72) 79 (54) 
 Intermediate 210 (21) 348 (24) 13 (14) 28 (19) 
 Advanced 0 (0) 0 (0) 14 (15) 40 (27) 
Cytogenetics     
 Good 35 (10) 108 (20) 6 (7) 10 (8) 
 Intermediate 255 (72) 331 (62) 63 (69) 92 (70) 
 Poor 64 (18) 97 (18) 22 (24) 29 (22) 
 Unknown, n 633 896 16 
Follow-up among survivors, mo    
 No. evaluated 440 759 48 74 
 Median (range) 38 (6-99) 46 (2-98) 36 (12-73) 36 (12-72) 
Donor KIR haplotype     
 AA 319 (32) 454 (32) 18 (22) 39 (29) 
 B/x 668 (68) 978 (68) 65 (78) 96 (71) 
Donor centromeric region score    
 AA 455 (46) 689 (48) 32 (39) 61 (45) 
 AB 442 (45) 594 (41) 43 (52) 58 (43) 
 BB 90 (9) 149 (10) 8 (10) 16 (12) 

Values are n (%) unless otherwise noted.

Bu, busulfan; Clof, clofarabine; Cy, cyclophosphamide; Flu, fludarabine.

We previously reported that MAC vs RIC intensity could differentially affect NK cell reconstitution,10,13  which in turn correlated with clinical outcomes. After combining the contemporaneous and KIR DS trial cohorts, we then analyzed the MAC and RIC groups separately. We also considered interactions between donor KIR and recipient C1 and C2 epitopes, which influence the education and function of donor NK cells and could therefore affect clinical outcomes.10,11  Recipient HLA-C types were similar in the 2 groups based on higher or lower intensity of conditioning, with homozygous expression of HLA-C2 group ligands (C2/C2) being observed in 15% of MAC patients vs 13% of the RIC patients (Table 2), similar to that observed in the general population. There were minor differences in the MAC recipients’ HLA matching across the C1 or C2 subsets, but no differences in any other clinical characteristics, such as graft type, disease status, or cytogenetic risk within either MAC or RIC recipients C1 or C2 subsets.

Table 2.

Recipient HLA C1 group phenotyping

MAC recipientsRIC recipients
VariableC1/C1, n (%)C1/C2, n (%)C2/C2, n (%)P*C1/C1, n (%)C1/C2, n (%)C2/C2, n (%)P*
No. of patients 638 (40) 696 (44) 244 (15)  435 (40) 515 (48) 131 (13)  
No. centers 98 97 80  86 86 61  
Age, median (range), y 49 (20-76) 49 (20-75) 48 (20-73) .84 64 (24-84) 64 (21-78) 64 (20-76) .73 
Donor recipient HLA allele matches    .01    .28 
 8/8 562 (88) 571 (82) 197 (81)  385 (89) 441 (86) 110 (84)  
 7/8 76 (12) 124 (18) 47 (19)  50 (11) 74 (14) 21 (16)  
HLA DP    .387    .606 
 Fully matched 112 (18) 116 (17) 40 (17)  72 (17) 81 (16) 25 (19)  
 Permissive mismatch 296 (47) 342 (50) 104 (43)  209 (49) 246 (49) 68 (53)  
 Nonpermissive mismatch 216 (35) 229 (33) 96 (40)  148 (34) 178 (35) 36 (28)  
Graft type        .72 
 Marrow 122 (19) 138 (20) 47 (19)  37 (9) 40 (8) 13 (10)  
 PBSC 516 (81) 558 (80) 197 (81)  398 (91) 475 (92) 118 (90)  
GVHD prophylaxis      
 Tac ± others 595 (93) 643 (92) 215 (88)  363 (83) 423 (82) 109 (83) .86 
 CSA ± others 42 (7) 53 (8) 29 (12)  72 (17) 91 (18) 22 (17)  
Conditioning regimen groups    .082    .887 
 RIC/NMA: TBI ± other     81 (19) 100 (19) 24 (18)  
 RIC/NMA: Flu/Clof ± other     156 (36) 197 (38) 51 (39)  
 RIC/NMA: alkylators     198 (46) 218 (42) 56 (43)  
 MAC: TBI ± Bu or Cy or other 129 (20) 110 (16) 49 (20)      
 MAC: non-TBI 509 (80) 586 (84) 195 (80)      
ATG/alemtuzumab use    .743    .292 
 ATG + alemtuzumab 1 (< 1) 0 (0) 0 (0)  0 (0) 0 (0) 0 (0)  
 ATG alone 234 (37) 261 (38) 97 (40)  158 (36) 201 (39) 52 (40)  
 Alemtuzumab alone 13 (2) 12 (2) 7 (3)  24 (6) 15 (3) 4 (3)  
 No ATG or alemtuzumab 389 (61) 423 (61) 140 (57)  253 (58) 299 (58) 74 (57)  
Disease status at transplant    .44    .53 
 Early 467 (73) 512 (74) 183 (75)  341 (78) 409 (79) 95 (73)  
 Intermediate 156 (24) 168 (24) 52 (21)  90 (21) 99 (19) 33 (25)  
 Advanced 13 (2) 16 (2) 9 (4)  4 (1) 6 (1) 3 (2)  
Recipient cytogenetics    .73    .81 
 Good 51 (19) 45 (16) 22 (19)  15 (9) 21 (9) 5 (11)  
 Intermediate 170 (62) 178 (64) 75 (66)  124 (71) 158 (71) 36 (77)  
 Poor 52 (19) 56 (20) 17 (15)  36 (21) 43 (19) 6 (13)  
Donor KIR haplotype        .17 
 AA 183 (29) 225 (32) 85 (35) .19 136 (32) 169 (33) 32 (25)  
 Bx 446 (71) 469 (68) 158 (65)  292 (68) 341 (67) 98 (75)  
Donor centromeric regions score    .11    .37 
 AA 281 (45) 349 (50) 120 (49)  189 (44) 243 (48) 54 (42)  
 AB 281 (45) 280 (40) 91 (37)  194 (45) 223 (44) 67 (52)  
 BB 67 (11) 65 (9) 32 (13)  45 (11) 44 (9) 9 (7)  
Year of transplant         
 2010 81 (13) 82 (12) 45 (18) .10 52 (12) 52 (10) 11 (8) .61 
 2011 90 (14) 93 (13) 28 (11)  43 (10) 63 (12) 23 (18)  
 2012 88 (14) 124 (18) 30 (12)  64 (15) 64 (12) 16 (12)  
 2013 114 (18) 102 (15) 40 (16)  67 (15) 89 (17) 17 (13)  
 2014 136 (21) 151 (22) 43 (18)  101 (23) 112 (22) 29 (22)  
 2015 119 (19) 128 (18) 54 (22)  95 (22) 117 (23) 29 (22)  
 2016 10 (2) 16 (2) 4 (2)  13 (3) 18 (3) 6 (5)  
Follow-up among survivors, mo         
 No. evaluated 337 375 120  201 233 53  
 Median (range) 42 (3-98) 46 (5-97) 45 (2-98) .61 39 (6-99) 38 (10-97) 36 (12-96) .48 
MAC recipientsRIC recipients
VariableC1/C1, n (%)C1/C2, n (%)C2/C2, n (%)P*C1/C1, n (%)C1/C2, n (%)C2/C2, n (%)P*
No. of patients 638 (40) 696 (44) 244 (15)  435 (40) 515 (48) 131 (13)  
No. centers 98 97 80  86 86 61  
Age, median (range), y 49 (20-76) 49 (20-75) 48 (20-73) .84 64 (24-84) 64 (21-78) 64 (20-76) .73 
Donor recipient HLA allele matches    .01    .28 
 8/8 562 (88) 571 (82) 197 (81)  385 (89) 441 (86) 110 (84)  
 7/8 76 (12) 124 (18) 47 (19)  50 (11) 74 (14) 21 (16)  
HLA DP    .387    .606 
 Fully matched 112 (18) 116 (17) 40 (17)  72 (17) 81 (16) 25 (19)  
 Permissive mismatch 296 (47) 342 (50) 104 (43)  209 (49) 246 (49) 68 (53)  
 Nonpermissive mismatch 216 (35) 229 (33) 96 (40)  148 (34) 178 (35) 36 (28)  
Graft type        .72 
 Marrow 122 (19) 138 (20) 47 (19)  37 (9) 40 (8) 13 (10)  
 PBSC 516 (81) 558 (80) 197 (81)  398 (91) 475 (92) 118 (90)  
GVHD prophylaxis      
 Tac ± others 595 (93) 643 (92) 215 (88)  363 (83) 423 (82) 109 (83) .86 
 CSA ± others 42 (7) 53 (8) 29 (12)  72 (17) 91 (18) 22 (17)  
Conditioning regimen groups    .082    .887 
 RIC/NMA: TBI ± other     81 (19) 100 (19) 24 (18)  
 RIC/NMA: Flu/Clof ± other     156 (36) 197 (38) 51 (39)  
 RIC/NMA: alkylators     198 (46) 218 (42) 56 (43)  
 MAC: TBI ± Bu or Cy or other 129 (20) 110 (16) 49 (20)      
 MAC: non-TBI 509 (80) 586 (84) 195 (80)      
ATG/alemtuzumab use    .743    .292 
 ATG + alemtuzumab 1 (< 1) 0 (0) 0 (0)  0 (0) 0 (0) 0 (0)  
 ATG alone 234 (37) 261 (38) 97 (40)  158 (36) 201 (39) 52 (40)  
 Alemtuzumab alone 13 (2) 12 (2) 7 (3)  24 (6) 15 (3) 4 (3)  
 No ATG or alemtuzumab 389 (61) 423 (61) 140 (57)  253 (58) 299 (58) 74 (57)  
Disease status at transplant    .44    .53 
 Early 467 (73) 512 (74) 183 (75)  341 (78) 409 (79) 95 (73)  
 Intermediate 156 (24) 168 (24) 52 (21)  90 (21) 99 (19) 33 (25)  
 Advanced 13 (2) 16 (2) 9 (4)  4 (1) 6 (1) 3 (2)  
Recipient cytogenetics    .73    .81 
 Good 51 (19) 45 (16) 22 (19)  15 (9) 21 (9) 5 (11)  
 Intermediate 170 (62) 178 (64) 75 (66)  124 (71) 158 (71) 36 (77)  
 Poor 52 (19) 56 (20) 17 (15)  36 (21) 43 (19) 6 (13)  
Donor KIR haplotype        .17 
 AA 183 (29) 225 (32) 85 (35) .19 136 (32) 169 (33) 32 (25)  
 Bx 446 (71) 469 (68) 158 (65)  292 (68) 341 (67) 98 (75)  
Donor centromeric regions score    .11    .37 
 AA 281 (45) 349 (50) 120 (49)  189 (44) 243 (48) 54 (42)  
 AB 281 (45) 280 (40) 91 (37)  194 (45) 223 (44) 67 (52)  
 BB 67 (11) 65 (9) 32 (13)  45 (11) 44 (9) 9 (7)  
Year of transplant         
 2010 81 (13) 82 (12) 45 (18) .10 52 (12) 52 (10) 11 (8) .61 
 2011 90 (14) 93 (13) 28 (11)  43 (10) 63 (12) 23 (18)  
 2012 88 (14) 124 (18) 30 (12)  64 (15) 64 (12) 16 (12)  
 2013 114 (18) 102 (15) 40 (16)  67 (15) 89 (17) 17 (13)  
 2014 136 (21) 151 (22) 43 (18)  101 (23) 112 (22) 29 (22)  
 2015 119 (19) 128 (18) 54 (22)  95 (22) 117 (23) 29 (22)  
 2016 10 (2) 16 (2) 4 (2)  13 (3) 18 (3) 6 (5)  
Follow-up among survivors, mo         
 No. evaluated 337 375 120  201 233 53  
 Median (range) 42 (3-98) 46 (5-97) 45 (2-98) .61 39 (6-99) 38 (10-97) 36 (12-96) .48 
*

The Pearson chi-square test was used for comparing discrete variables and Kruskal-Wallis for continuous variables.

Clinical outcomes

The overall unadjusted univariate outcomes for RIC vs MAC patients were similar, suggesting there were no underlying differences in selection between the contemporaneous and KIR DS trial cohorts (Table 3). Nearly all (98% to 99%) patients engrafted (data not shown) and only 11% to 13% died of nonrelapse, transplant-related mortality (NRM) by 6 months. The incidences of relapse based on conditioning (RIC vs MAC) were not significantly different in the 2 cohorts, leading to estimated 5-year survival rates of 39% and 44% in the RIC recipients and 49% and 45% in the MAC recipients for the contemporaneous and KIR DS trial cohorts, respectively. Similar 5-year DFS rates were observed (35% and 40% after RIC and 46% and 38% after MAC). None of these minor outcome differences between the prospective and retrospective cohorts were significant in either conditioning intensity subset. Because the demographic profiles and key clinical outcomes were consistent for the contemporaneous and KIR DS trial cohorts, we combined them to test the effect of donor KIR haplotypes on clinical outcome, without significant bias. Statistical interactions between the prospective group and the contemporaneous, nonoverlapping larger retrospective cohort were tested for all reported outcomes.

Table 3.

Post-HCT outcomes

Contemporaneous cohortProspective KIR DS trial
RICMACRICMAC
nProbability (95% CI)nProbability (95% CI)nProbability (95% CI)nProbability (95% CI)
Relapse 986  1431  96  147  
 At 5 y  37 (33-40)  31 (28-33)  37 (27-47)  40 (31-49) 
NRM 986  1427  96  146  
 At 6 mo  11 (9-13)  11 (9-12)  13 (7-20)  11 (6-16) 
DFS 986  1427  96  144  
 At 5 y  35 (31-38)  46 (43-49)  40 (30-51)  38 (28-48) 
Overall survival 987  1431  96  147  
 At 5 y  39 (35-43)  49 (46-52)  44 (33-55)  45 (36-54) 
Contemporaneous cohortProspective KIR DS trial
RICMACRICMAC
nProbability (95% CI)nProbability (95% CI)nProbability (95% CI)nProbability (95% CI)
Relapse 986  1431  96  147  
 At 5 y  37 (33-40)  31 (28-33)  37 (27-47)  40 (31-49) 
NRM 986  1427  96  146  
 At 6 mo  11 (9-13)  11 (9-12)  13 (7-20)  11 (6-16) 
DFS 986  1427  96  144  
 At 5 y  35 (31-38)  46 (43-49)  40 (30-51)  38 (28-48) 
Overall survival 987  1431  96  147  
 At 5 y  39 (35-43)  49 (46-52)  44 (33-55)  45 (36-54) 

Kaplan-Meier or competing hazards (relapse, NRM) estimates of outcomes with 95% CIs.

Donor KIR B haplotypes provide relapse protection after RIC HCT

We previously reported that enhanced relapse protection and superior DFS are associated with donor KIR B haplotype in recipients of MAC URD HCT,8-10  but we had not examined this question in the RIC setting. In addition, HCT procedures (and outcomes) have changed over time, reflecting progress in the field and highlighting the importance for analysis of considering the era in which the transplants were performed.16  Notably, the previously studied cohorts8-10  had markedly different demographics than the 2010 to 2016 cohort reported here. In our prior analyses, there were 1532 younger patients (median age, 38) with AML, all receiving MAC URD HCT between 1988 and 2009. Only 57% were HLA 8/8 allele matched; 53% received marrow grafts and a larger fraction (32% vs 2%) had advanced-stage AML (supplemental Table 1). The use of RIC, fully matched donors, and PBSC grafts were all substantially more frequent in the 2010 to 2016 cohort of HCTs. Consistent with improvements in the procedures of HCT and HLA matching, the overall outcomes were also improved in the more recently transplanted groups of patients.

In the combined 2010 to 2016 cohort, all multivariate analyses were adjusted for relevant covariates and for KIR genotyping variables. For the 1087 patients receiving RIC, use of a KIR B haplotype donor (Bx vs AA) significantly reduced the risk for relapse (hazard ratio [HR], 0.77; 95% confidence interval [CI], 0.62-0.97;P = .026; Table 4) and was nearly identical (HR, 0.78; 95% CI, 0.63-0.97, P = .027) if we excluded the prospective cohort. The favorable effect of the KIR B haplotype on relapse was significant in the fully HLA 8/8 matched group even after excluding the prospective smaller cohort (HR, 0.79; 95% CI, 0.63-0.98; P = .033 for Bx vs AA). Bx donors yielded improved DFS (HR, 0.84; 95% CI, 0.72-0.99; P = .038; Table 4) and led to small effects in improving OS (HR, 0.85; 95% CI, 0.71-1.01; P = .069; supplemental Table 2A), whereas having no significant influence on NRM or GVHD in the combined or only the retrospective cohort (data not shown). For the retrospective MAC cohort, we found that donors homozygous for centromeric KIR B haplotype groups were particularly effective in preventing relapse.9  Among the RIC group, the protection afforded by donors with centromeric KIR B genes was similar for Cen AB and Cen BB and stronger than that observed with Cen AA donors. The combined Cen AB and Cen BB donors vs Cen AA donors has a HR of 0.77 (95% CI, 0.62-0.96; P = .018) for relapse and HR of 0.81 (95% CI, 0.69-0.95; P = .010) for DFS. There were no significant interactions between these RIC donor effects prospective KIR DS cohort and the larger group for all end points studied.

Table 4.

Reduced intensity conditioning

FactornEventHRHR lowHR upperP
Relapse       
 Donor KIR haplotype      .026* 
  AA 334 130    
  BX 730 240 0.77 0.62 0.97 .026 
 Cytogenetics      .0025* 
 Disease status      .0001* 
  Early 837 277    
  Intermediate 218 87 1.34 1.05 1.72 .019 
  Advanced 3.97 1.88 8.36 .0003 
ATG/alemtuzumab      .021 
  No ATG/alemtuzumab 617 207 1.00    
  ATG alone 404 155 1.18 0.88 1.56 .28 
  Alemtuzumab alone 43 0.59 0.36 0.96 .035 
 HLA-DP mismatch      .54 
  Fully matched 178 66 1.00    
  Mismatch 872 299 0.99 0.73 1.24 .94 
  Missing 14 1.29 0.77 2.15 .33 
 Donor KIR centromeric regions      .051* 
  AA 483 183 1.00    
  AB 483 155 0.77 0.61 0.98 .035 
  BB 98 32 0.77 0.54 1.09 .14 
 Cytogenetics      .0024* 
 Disease status      <.0001* 
  Early 837 277 1.00    
  Intermediate 218 87 1.37 1.06 1.75 .014 
  Advanced 4.08 1.95 8.51 .0002 
ATG/alemtuzumab      .029 
  No ATG/alemtuzumab 617 207 1.00    
  ATG alone 404 155 1.16 0.87 1.54 .32 
  Alemtuzumab alone 43 0.59 0.36 0.98 .043 
  HLA-DP mismatch      .49 
  Fully matched 178 66 1.00    
  Mismatch 872 299 0.98 0.72 1.33 .89 
  Missing 14 1.30 0.78 2.15 .31 
DFS       
 KIR B haplotype      .038 
  AA 334 214 1.00    
  BX 728 423 0.84 0.72 0.99 .038 
 HLA matched alleles      .042 
  7/8 145 106 1.00    
  8/8 917 531 0.78 0.61 0.99 .042 
 Cytogenetics      .0012 
 Donor age      .053 
 Disease status      .022 
  Early 836 487 1.00    
  Intermediate 218 142 1.18 0.98 1.43 .085 
  Advanced 3.01 1.22 7.40 .017 
 Recipient age, y      .20 
  20-29 23 13 1.00    
  30-39 29 15 0.69 0.33 1.44 .32 
  40-49 57 33 0.98 0.52 1.83 .95 
  50-59 198 116 0.97 0.58 1.64 .92 
  ≥60 755 460 1.07 0.64 1.80 .80 
 Recipient CMV status      .035 
 ATG/alemtuzumab      .31 
  No ATG/alemtuzumab 615 363 1.00    
  ATG alone 404 245 1.04 0.85 1.27 .71 
  Alemtuzumab alone 43 29 1.22 0.95 1.58 .12 
HLA-DP mismatch      .10 
  Fully matched 178 109 1.00    
  Mismatch 871 519 1.06 0.84 1.34 .64 
  Missing 13 1.69 1.10 2.60 .017 
 Donor KIR centromeric regions      .034 
  AA 482 308 1.00    
  AB 483 278 0.82 0.70 0.96 .016 
  BB 97 51 0.76 0.56 1.02 .069 
 HLA matched alleles      .057 
  7/8 145 106 1.00    
  8/8 917 531 0.79 0.61 1.01 .057 
 Cytogenetics      .0009 
 Donor age      .054 
 Disease status      .013 
  Early 836 487 1.00    
  Intermediate 218 142 1.20 0.99 1.45 .064 
  Advanced 3.06 1.28 7.31 .012 
 Recipient age, y       
  20-29 23. 13 1.00    
  30-39 29 15 0.68 0.32 1.44 .31 
  40-49 57 33 0.96 0.52 1.80 .91 
  50-59 198 116 0.96 0.57 1.62 .88 
  ≥60 755 460 1.05 0.62 1.77 .85 
 Recipient CMV status      .052 
 ATG/alemtuzumab      .25 
  No ATG/alemtuzumab 615 363 1.00    
  ATG alone 404 245 1.03 0.84 1.26 .79 
  Alemtuzumab alone 43 29 1.24 0.96 1.60 .10 
 HLA-DP mismatch      .036 
  Fully matched 178 109 1.00    
  Mismatch 871 519 1.05 0.83 1.33 .66 
  Missing 13 1.71 1.13 2.58 .011 
FactornEventHRHR lowHR upperP
Relapse       
 Donor KIR haplotype      .026* 
  AA 334 130    
  BX 730 240 0.77 0.62 0.97 .026 
 Cytogenetics      .0025* 
 Disease status      .0001* 
  Early 837 277    
  Intermediate 218 87 1.34 1.05 1.72 .019 
  Advanced 3.97 1.88 8.36 .0003 
ATG/alemtuzumab      .021 
  No ATG/alemtuzumab 617 207 1.00    
  ATG alone 404 155 1.18 0.88 1.56 .28 
  Alemtuzumab alone 43 0.59 0.36 0.96 .035 
 HLA-DP mismatch      .54 
  Fully matched 178 66 1.00    
  Mismatch 872 299 0.99 0.73 1.24 .94 
  Missing 14 1.29 0.77 2.15 .33 
 Donor KIR centromeric regions      .051* 
  AA 483 183 1.00    
  AB 483 155 0.77 0.61 0.98 .035 
  BB 98 32 0.77 0.54 1.09 .14 
 Cytogenetics      .0024* 
 Disease status      <.0001* 
  Early 837 277 1.00    
  Intermediate 218 87 1.37 1.06 1.75 .014 
  Advanced 4.08 1.95 8.51 .0002 
ATG/alemtuzumab      .029 
  No ATG/alemtuzumab 617 207 1.00    
  ATG alone 404 155 1.16 0.87 1.54 .32 
  Alemtuzumab alone 43 0.59 0.36 0.98 .043 
  HLA-DP mismatch      .49 
  Fully matched 178 66 1.00    
  Mismatch 872 299 0.98 0.72 1.33 .89 
  Missing 14 1.30 0.78 2.15 .31 
DFS       
 KIR B haplotype      .038 
  AA 334 214 1.00    
  BX 728 423 0.84 0.72 0.99 .038 
 HLA matched alleles      .042 
  7/8 145 106 1.00    
  8/8 917 531 0.78 0.61 0.99 .042 
 Cytogenetics      .0012 
 Donor age      .053 
 Disease status      .022 
  Early 836 487 1.00    
  Intermediate 218 142 1.18 0.98 1.43 .085 
  Advanced 3.01 1.22 7.40 .017 
 Recipient age, y      .20 
  20-29 23 13 1.00    
  30-39 29 15 0.69 0.33 1.44 .32 
  40-49 57 33 0.98 0.52 1.83 .95 
  50-59 198 116 0.97 0.58 1.64 .92 
  ≥60 755 460 1.07 0.64 1.80 .80 
 Recipient CMV status      .035 
 ATG/alemtuzumab      .31 
  No ATG/alemtuzumab 615 363 1.00    
  ATG alone 404 245 1.04 0.85 1.27 .71 
  Alemtuzumab alone 43 29 1.22 0.95 1.58 .12 
HLA-DP mismatch      .10 
  Fully matched 178 109 1.00    
  Mismatch 871 519 1.06 0.84 1.34 .64 
  Missing 13 1.69 1.10 2.60 .017 
 Donor KIR centromeric regions      .034 
  AA 482 308 1.00    
  AB 483 278 0.82 0.70 0.96 .016 
  BB 97 51 0.76 0.56 1.02 .069 
 HLA matched alleles      .057 
  7/8 145 106 1.00    
  8/8 917 531 0.79 0.61 1.01 .057 
 Cytogenetics      .0009 
 Donor age      .054 
 Disease status      .013 
  Early 836 487 1.00    
  Intermediate 218 142 1.20 0.99 1.45 .064 
  Advanced 3.06 1.28 7.31 .012 
 Recipient age, y       
  20-29 23. 13 1.00    
  30-39 29 15 0.68 0.32 1.44 .31 
  40-49 57 33 0.96 0.52 1.80 .91 
  50-59 198 116 0.96 0.57 1.62 .88 
  ≥60 755 460 1.05 0.62 1.77 .85 
 Recipient CMV status      .052 
 ATG/alemtuzumab      .25 
  No ATG/alemtuzumab 615 363 1.00    
  ATG alone 404 245 1.03 0.84 1.26 .79 
  Alemtuzumab alone 43 29 1.24 0.96 1.60 .10 
 HLA-DP mismatch      .036 
  Fully matched 178 109 1.00    
  Mismatch 871 519 1.05 0.83 1.33 .66 
  Missing 13 1.71 1.13 2.58 .011 

Stratified variables: Karnofsky performance score. Poor risk cytogenetics significantly associated with risks of relapse in RIC and MAC adjusted for other covariates. Bolded P values are independently significant P < .05.

*

Adjusted multivariate analysis for the end points shown stratified as indicated.

No significant associations between donor telomeric KIR haplotypes and NRM or GVHD outcomes were observed (data not shown). Additionally, neither ATG/alemtuzumab use nor permissive (or nonpermissive) mismatching for HLA-DP (clinical elements previously reported to influence HCT outcomes) had significant influence on relapse in RIC recipients (Table 4).

In marked contrast to our earlier analyses,8-10  this evaluation of 1552 MAC transplants found no significant influence of donor KIR B haplotypes on any of the clinical end points, including OS, DFS, relapse, NRM, acute or chronic GVHD, and engraftment (Table 5 [DFS, relapse]; supplemental Table 2B [OS]), and data not shown (NRM, GVHD). Additionally, there were no significant interactions between the prospective KIR DS cohort and the larger group. As expected, cytogenetics and disease status significantly influenced the risk of relapse for patients in both the RIC and MAC cohorts, confirming the dominance of underlying disease characteristics to predict disease control with URD HCT in the current era.

Table 5.

Myeloablative conditioning

FactornEventHRHR lowHR upperP
Relapse       
 Donor KIR haplotype      .77* 
  AA 490 153 1.00    
  BX 1060 306 0.97 0.82 1.16 .77 
 Cytogenetics      .0035* 
 Disease status      <.0001* 
  Early 1148 337 1.00    
  Intermediate 370 104 1.09 0.86 1.38 .4822 
  Advanced 32 18 3.93 1.90 8.14 .0002 
 ATG/alemtuzumab      .019 
  No ATG/alemtuzumab 930 258 1.00    
  ATG alone 589 190 1.25 1.05 1.49 .012 
  Alemtuzumab alone 31 11 1.43 0.85 2.40 .18 
 HLA-DP mismatch      .55 
  Fully matched 267 84 1.00    
  Mismatch 1264 370 0.92 0.76 1.12 .42 
  Missing 19 0.74 0.39 1.40 .35 
 Donor KIR centromeric regions      .23* 
  AA 744 237 1.00    
  AB 644 173 0.86 0.73 1.02 .093 
  BB 162 49 1.03 0.77 1.37 .86 
 Cytogenetics      .0045* 
 Disease status      .0003 
  Early 1148 337 1.00    
  Intermediate 370 104 1.09 0.86 1.38 .50 
  Advanced 32 18 4.02 1.94 8.33 .0002 
 ATG/alemtuzumab      .016 
  No ATG/alemtuzumab 930 258 1.00    
  ATG alone 589 190 1.26 1.06 1.50 .010 
  Alemtuzumab alone 31 11 1.42 0.86 2.33 .17 
 HLA-DP mismatch      .57 
  Fully matched 267 84 1.00    
  Mismatch 1264 370 0.93 0.77 1.12 .44 
  Missing 19 0.74 0.39 1.41 .36 
DFS       
 KIR B haplotype      .40 
  AA 489 245 1.00    
  BX 1057 541 1.07 0.91 1.25 .40 
 HLA matched alleles      .0078 
  7/8 245 141 1.00    
  8/8 1301 645 0.77 0.63 0.93 .0078 
 Cytogenetics      .0041 
 Donor age      .40 
 Disease status      <.0001 
  Early 1147 566 1.00    
  Intermediate 369 196 1.20 1.03 1.40 .019 
  Advanced 30 24 2.76 1.60 4.77 .0003 
 Recipient age, y      .0058 
  20-29 194 78 1.00    
  30-39 251 119 1.23 0.97 1.55 .084 
  40-49 367 175 1.26 0.95 1.65 .10 
  50-59 467 247 1.41 1.11 1.77 .0040 
  ≥60 267 167 1.72 1.27 2.32 .0005 
 Recipient CMV status      .23 
 ATG/alemtuzumab      .81 
  No ATG/alemtuzumab 929 474 1.00    
  ATG alone 586 295 1.02 0.89 1.17 .79 
  Alemtuzumab alone 31 17 1.16 0.72 1.87 .53 
 HLA-DP mismatch      .78 
  Fully matched 265 141 1.00    
  Mismatch 1262 635 0.95 0.81 1.11 .49 
  Missing 19 10 0.93 0.59 1.46 .74 
 Donor KIR centromeric regions      .72 
  AA 742 382 1.00    
  AB 643 321 0.99 0.84 1.17 .93 
  BB 161 83 1.09 0.88 1.36 .44 
 HLA matched alleles      .0066 
  7/8 245 141 1.00    
  8/8 1301 645 0.76 0.63 0.93 .0066 
 Cytogenetics      .0043 
 Donor age      .39 
 Disease status      <.0001 
  Early 1147 566 1.00    
  Intermediate 369 196 1.20 1.03 1.40 .021 
  Advanced 30 24 2.79 1.61 4.81 .0002 
 Recipient age, y      .0053 
  20-29 194 78 1.00    
  30-39 251 119 1.23 0.97 1.55 .082 
  40-49 367 175 1.26 0.96 1.65 .098 
  50-59 467 247 1.41 1.12 1.77 .0036 
  ≥60 267 167 1.73 1.27 2.34 .0004 
 Recipient CMV status      .24 
 ATG/alemtuzumab      .83 
  No ATG/alemtuzumab 929 474 1.00    
  ATG alone 586 295 1.03 0.89 1.18 .73 
  Alemtuzumab alone 31 17 1.16 0.72 1.87 .55 
 HLA-DP mismatch      .80 
  Fully matched 265 141 1.00    
  Mismatch 1262 635 0.95 0.81 1.11 .51 
  Missing 19 10 0.94 0.60 1.47 .77 
FactornEventHRHR lowHR upperP
Relapse       
 Donor KIR haplotype      .77* 
  AA 490 153 1.00    
  BX 1060 306 0.97 0.82 1.16 .77 
 Cytogenetics      .0035* 
 Disease status      <.0001* 
  Early 1148 337 1.00    
  Intermediate 370 104 1.09 0.86 1.38 .4822 
  Advanced 32 18 3.93 1.90 8.14 .0002 
 ATG/alemtuzumab      .019 
  No ATG/alemtuzumab 930 258 1.00    
  ATG alone 589 190 1.25 1.05 1.49 .012 
  Alemtuzumab alone 31 11 1.43 0.85 2.40 .18 
 HLA-DP mismatch      .55 
  Fully matched 267 84 1.00    
  Mismatch 1264 370 0.92 0.76 1.12 .42 
  Missing 19 0.74 0.39 1.40 .35 
 Donor KIR centromeric regions      .23* 
  AA 744 237 1.00    
  AB 644 173 0.86 0.73 1.02 .093 
  BB 162 49 1.03 0.77 1.37 .86 
 Cytogenetics      .0045* 
 Disease status      .0003 
  Early 1148 337 1.00    
  Intermediate 370 104 1.09 0.86 1.38 .50 
  Advanced 32 18 4.02 1.94 8.33 .0002 
 ATG/alemtuzumab      .016 
  No ATG/alemtuzumab 930 258 1.00    
  ATG alone 589 190 1.26 1.06 1.50 .010 
  Alemtuzumab alone 31 11 1.42 0.86 2.33 .17 
 HLA-DP mismatch      .57 
  Fully matched 267 84 1.00    
  Mismatch 1264 370 0.93 0.77 1.12 .44 
  Missing 19 0.74 0.39 1.41 .36 
DFS       
 KIR B haplotype      .40 
  AA 489 245 1.00    
  BX 1057 541 1.07 0.91 1.25 .40 
 HLA matched alleles      .0078 
  7/8 245 141 1.00    
  8/8 1301 645 0.77 0.63 0.93 .0078 
 Cytogenetics      .0041 
 Donor age      .40 
 Disease status      <.0001 
  Early 1147 566 1.00    
  Intermediate 369 196 1.20 1.03 1.40 .019 
  Advanced 30 24 2.76 1.60 4.77 .0003 
 Recipient age, y      .0058 
  20-29 194 78 1.00    
  30-39 251 119 1.23 0.97 1.55 .084 
  40-49 367 175 1.26 0.95 1.65 .10 
  50-59 467 247 1.41 1.11 1.77 .0040 
  ≥60 267 167 1.72 1.27 2.32 .0005 
 Recipient CMV status      .23 
 ATG/alemtuzumab      .81 
  No ATG/alemtuzumab 929 474 1.00    
  ATG alone 586 295 1.02 0.89 1.17 .79 
  Alemtuzumab alone 31 17 1.16 0.72 1.87 .53 
 HLA-DP mismatch      .78 
  Fully matched 265 141 1.00    
  Mismatch 1262 635 0.95 0.81 1.11 .49 
  Missing 19 10 0.93 0.59 1.46 .74 
 Donor KIR centromeric regions      .72 
  AA 742 382 1.00    
  AB 643 321 0.99 0.84 1.17 .93 
  BB 161 83 1.09 0.88 1.36 .44 
 HLA matched alleles      .0066 
  7/8 245 141 1.00    
  8/8 1301 645 0.76 0.63 0.93 .0066 
 Cytogenetics      .0043 
 Donor age      .39 
 Disease status      <.0001 
  Early 1147 566 1.00    
  Intermediate 369 196 1.20 1.03 1.40 .021 
  Advanced 30 24 2.79 1.61 4.81 .0002 
 Recipient age, y      .0053 
  20-29 194 78 1.00    
  30-39 251 119 1.23 0.97 1.55 .082 
  40-49 367 175 1.26 0.96 1.65 .098 
  50-59 467 247 1.41 1.12 1.77 .0036 
  ≥60 267 167 1.73 1.27 2.34 .0004 
 Recipient CMV status      .24 
 ATG/alemtuzumab      .83 
  No ATG/alemtuzumab 929 474 1.00    
  ATG alone 586 295 1.03 0.89 1.18 .73 
  Alemtuzumab alone 31 17 1.16 0.72 1.87 .55 
 HLA-DP mismatch      .80 
  Fully matched 265 141 1.00    
  Mismatch 1262 635 0.95 0.81 1.11 .51 
  Missing 19 10 0.94 0.60 1.47 .77 

Stratified variables: Karnofsky performance score. Poor risk cytogenetics significantly associated with risks of Relapse in RIC and MAC adjusted for other covariates. Bolded P values are independently significant P < .05.

*

Adjusted multivariate analysis for the end points shown stratified as indicated.

DFS was significantly improved in patients with HLA-matched donors and in patients with early or intermediate AML disease status. Age and the recipients’ CMV serostatus were not independently associated with DFS, although younger age favored better OS after MAC HCT (Table 5; supplemental Table 3B). None of the other donor KIR parameters influenced the risks of NRM, acute or chronic GVHD or the time to neutrophil engraftment (data not shown) and there were no significant interactions between the KIR B haplotype and HLA 8/8 matching for any of the end points studied.

Recipients with C1 epitopes of HLA-C benefit most from donor KIR B haplotype HCTs

In this analysis, we observed that donor KIR B haplotypes were favorable for RIC HCTs, but not for MAC HCTs. Therefore, we explored the RIC group further. The education and long-term functional response of NK cells is strongly influenced by interactions between inhibitory KIR receptors and self-HLA class I. KIR2DL1/S1 recognizes HLA-C2, whereas KIR2DL2/L3 recognizes HLA-C1 and KIR3DL1 recognizes Bw4. We evaluated the 935 RIC recipients (Table 6; Figure 1) having at least 1 C1 epitope of HLA-C (C1/x) compared with those homozygous for HLA-C2 (C2/C2). The strong relapse protection with donor KIR Bx haplotypes is maintained in HLA-C1/x recipients (HR, 0.76; 95% CI, 0.61-0.97; P = .024, Table 6). In marked contrast, no protective effect of KIR Bx haplotypes for C2/C2 recipients was observed (Table 6). No effects of recipient C1/x and/or donor B haplotype on outcomes were observed for the MAC HCT recipients (data not shown).

Table 6.

Recipient C1/x and donor KIR B haplotype in reduced intensity conditioning HCT

Recipient C1/xRecipient C2/C2
 FactornHR95% CIPnHR95% CIP
Relapse         
 Donor KIR haplotype    .037*    .57* 
  AA 302   32   
  BX 631 0.78 0.62-0.98 .037 97 0.82 0.40-1.65 .57 
 Donor KIR B centromeric regions    .042*    .21* 
  AA 428   54   
  AB 416 0.80 0.62-1.02 .071 66 0.80 0.40-1.62 .54 
  BB 89 0.70 0.49-1.01 .055 1.74 0.67-4.52 .25 
DFS     
 Donor KIR B haplotype    .040*    .36* 
  AA 302   32   
  BX 629 0.85 0.72-0.99 .040 97 0.80 0.50-1.29 .36 
 Donor KIR B centromeric regions        .66* 
  AA 427   54   
  AB 416 0.82 0.69-0.98 .030 66 0.82 0.49-1.37 .45 
  BB 88 0.74 0.54-1.01 .060 1.17 0.54-2.56 .68 
Overall survival     
 Donor KIR haplotype        .87* 
  AA 304   32   
  BX 631 0.82 0.68-0.98 .029 97 0.96 0.58-1.57 .87 
 Donor KIR B centromeric regions    .13*    .77* 
  AA 430   54   
  AB 416 0.85 0.71-1.01 .067 66 0.84 0.49-1.43 .52 
  BB 89 0.75 0.52-1.08 .12 1.18 0.49-2.83 .71 
Recipient C1/xRecipient C2/C2
 FactornHR95% CIPnHR95% CIP
Relapse         
 Donor KIR haplotype    .037*    .57* 
  AA 302   32   
  BX 631 0.78 0.62-0.98 .037 97 0.82 0.40-1.65 .57 
 Donor KIR B centromeric regions    .042*    .21* 
  AA 428   54   
  AB 416 0.80 0.62-1.02 .071 66 0.80 0.40-1.62 .54 
  BB 89 0.70 0.49-1.01 .055 1.74 0.67-4.52 .25 
DFS     
 Donor KIR B haplotype    .040*    .36* 
  AA 302   32   
  BX 629 0.85 0.72-0.99 .040 97 0.80 0.50-1.29 .36 
 Donor KIR B centromeric regions        .66* 
  AA 427   54   
  AB 416 0.82 0.69-0.98 .030 66 0.82 0.49-1.37 .45 
  BB 88 0.74 0.54-1.01 .060 1.17 0.54-2.56 .68 
Overall survival     
 Donor KIR haplotype        .87* 
  AA 304   32   
  BX 631 0.82 0.68-0.98 .029 97 0.96 0.58-1.57 .87 
 Donor KIR B centromeric regions    .13*    .77* 
  AA 430   54   
  AB 416 0.85 0.71-1.01 .067 66 0.84 0.49-1.43 .52 
  BB 89 0.75 0.52-1.08 .12 1.18 0.49-2.83 .71 
*

Overall P value.

Other researchers have reported improved survival for HCT patients having at least 1 HLA C1 epitope compared with C2/C2 homozygous patients,11,17-19  particularly if the donor also has KIR2DS1.12,20  In adjusted multivariate analysis, we observed that donor KIR2DS3 and 2DL5 genes defining B haplotypes provide significant protection against relapse in RIC HCT (supplemental Table 3A). The other KIR B-defining genes had similar effects on relapse that did not reach statistical significance. These effects were not apparent in the absence of the C1 epitope of HLA-C (supplemental Table 3B). No relapse protection was observed in recipients homozygous for C2 epitopes (all P > .48; data not shown), although the small size of the C2 homozygous cohort precludes definitive analysis. In RIC HCTs, similarly favorable relative risks (RR) for improved DFS were observed with KIR2DS3 (supplemental Table 3A). Donor KIR2DS3 conferred the strongest association with protection against relapse (RR, 0.61; 95% CI, 0.47-0.79; P = .0001) and DFS (RR, 0.76; 95% CI, 0.62-0.92; P = .0054). Like the other KIR B genes, donor KIR2DS1 and other KIR B defining genes were associated with relapse protection, yet these effects were not significant after adjustment for multiple testing. Donor KIR2DS1 was not associated with significant effects on DFS or OS. In MAC HCT, none of the individual genes that define KIR B showed any effect on relapse, DFS, or OS (supplemental Table 3A) either in the whole cohort or in those with C1/x recipients (supplemental Table 3B).

Discussion

The interaction of donor KIR and recipient class I HLA in URD transplantation for AML is complex. As we previously reported, the donor KIR B haplotype and particularly the Cen B region reduce the risk of relapse and improve DFS.8-10,13  In the analysis reported here, the beneficial effect of donor KIR B haplotypes was observed only for the transplant patients given RIC, whereas no significant KIR gene associations with outcome were observed for MAC transplants. The different results obtained in this study (2010-2016) compared with the earlier cohort (1988-2009), which comprised only MAC HCTs,8-10  prompted us to examine the demographic features that distinguish the 2 transplant cohorts (supplemental Table 1).

Consistent with current practice standards for HCT, 40% of the later cohort received RIC. The recipients were all older, but they rarely had advanced disease status or poor risk cytogenetics. In addition, almost all HCTs in the later cohort were performed using filgrastim-mobilized PBSC rather than bone marrow stem cells. Compared with the earlier cohort,8-10  the MAC recipients in the later cohort were older and almost all of them received PBSC grafts. These recipients rarely had advanced disease, which intrinsically reduced their risk of relapse.

In comparing the 2 eras of transplantation, the overall relapse rate for MAC HCTs improved from 34% at 3 years in the earlier cohort to a 29% 3-year relapse incidence in the current cohort. Similar improvement was not observed for the RIC transplants, for which the 3-year relapse incidence RIC recipients was 34%. Improvements in transplant platforms and more favorable risk patients being transplanted explains in part, whereas KIR B haplotype donors did not reduce risks in MAC transplants. Additionally, NRM in the earlier cohort (27% at 1 year) vs the current cohort (15% to 16% at 1 year) has improved, limiting the competing hazard for relapse. Other studies evaluating the role of donor KIR in HCT have reported protection from relapse of AML and other hematologic malignancies,17,19,21,22  as well as associations with increased risk of GVHD, a correlation we did not see in the large cohort studied here.19,21,23,24 

Our earlier analyses demonstrated a stronger protection from relapse for KIR B haplotype donors, for recipients having the C1 epitope, and for patients receiving an HLA-C-mismatched transplant including a mismatch for HLA-C1/C2.10  In the current cohort, HLA mismatching was relatively rare (∼15%) and HLA-C mismatch was uncommon, precluding a meaningful examination of HLA-C mismatch. However, RIC recipients having C1 and a KIR B donor exhibited a strong relapse protection in comparison with HLA-C2 homozygous recipients. Each of the donor KIR B genes was correlated with C1 epitope-mediated protection from relapse. No comparable effect was detected in the MAC HCTs in which the relapse rate was already reduced compared with earlier cohorts.

This analysis of a large cohort of modern URD transplants for AML confirms that strong relapse protection is associated with RIC, donor KIR B haplotype, and donor KIR Cen B, but not KIR Tel B. Donors with these strikingly favorable KIR profiles were associated with a 24% reduction in relapse and 23% improvement in DFS. Such protection was not observed in C2/C2 homozygous RIC patients and was not observed in MAC transplants.

In the prospective KIR DS trial,13  only 40% of the 243 enrolled patients received RIC HCT based on clinical choices made by the participating transplant centers, thus limiting statistical power to determine whether donor KIR B haplotypes influence relapse protection. However, analysis of the 992 RIC recipients gave definitive results demonstrating that KIR B donors protect against AML relapse. We also hypothesize that NK cell reconstitution could influence current vs early analyses. We have recently shown that graft source (marrow vs granulocyte colony-stimulating factor mobilized peripheral blood) can modify the adaptive NK cell response to CMV.25  Differences in HLA matching strategies and KIR choice considerations have also been reported to modify relapse risk.21,26,27  Last, other peritransplant variables and supportive care protocol improvements could also be immunologically important.

In the current era of transplantation, the benefit of donor KIR B haplotypes involves all the KIR B defining genes and is most important for HCT using RIC, where relapse rates are higher. The relapse protection is particularly strong in the large population (∼85%) of recipients carrying at least 1 copy of the HLA-C1 epitope. We propose that this knowledge is directly applicable to donor selection today. Independent replication of this observation plus further genetic and translational studies should advance patient care and improve clinical outcomes. Methods for high-throughput KIR genotyping are now widely available and can increase the pool of fully characterized donors. When given the choice between otherwise comparable URD, we conclude that there is no disadvantage, and significant potential advantage, in choosing a KIR B haplotype donor to decrease post-HCT relapse of AML.

Data may be requested through e-mail to the corresponding author (mille011@umn.edu).

Acknowledgments

This work was supported by National Institutes of Health, National Cancer Institute (NCI) grants P01 CA111412 (D.W., T.W., T.A.F., E.K.W., S.G.E.M, P.P., L.A.G., and J.S.M.), P50 CA171963 (T.A.F.), R01 CA205239 (T.A.F.), and in part by P30 CA77598 using the Masonic Cancer Center Oncology Medical Informatics shared resource. The Center for International Blood and Marrow Transplant Research is supported primarily by Public Health Service Grant/Cooperative Agreement U24CA076518 from the NCI, the National Heart, Lung and Blood Institute (NHLBI), and the National Institute of Allergy and Infectious Diseases; a grant/cooperative agreement from NHLBI and NCI; NCI grant U24CA233032-01; NHLBI grants 5U24HL138660-02 and U01HL128568; Health Resources and Services Administration contract HHSH250201700006C; and Office of Naval Research grants N00014-18-1-2888 and N00014-17-1-2850, and others.

The views expressed in this article do not reflect the official policy or position of the National Institutes of Health, the Department of the Navy, the Department of Defense, or any other agency of the US Government.

Authorship

Contribution: D.W., S.C., S.S., S.G.E.M., P.P., L.A.G., and J.S.M. designed this study, analyzed data, and wrote the manuscript; C.V.-G., J.A.S., A.S., J.V., and T.W. collected data and performed the biostatistical analysis for this study and wrote the manuscript; and E.T., T.A.F., A.E.W., S.M.D., M.R., E.K.W., R.M.S., J.M., B.O., S.S.F., T.S., and K.V.B. assisted with data interpretation and assisted in writing the manuscript.

Conflict-of-interest disclosure: The authors declare no competing financial interests.

Correspondence: Jeffrey S. Miller, University of Minnesota, 420 Delaware St SE, Minneapolis, MN 55455; e-mail: mille011@umn.edu.

References

References
1.
Farag
SS
,
Fehniger
TA
,
Ruggeri
L
,
Velardi
A
,
Caligiuri
MA
.
Natural killer cell receptors: new biology and insights into the graft-versus-leukemia effect
.
Blood
.
2002
;
100
(
6
):
1935
-
1947
.
2.
Cooley
S
,
McCullar
V
,
Wangen
R
, et al
.
KIR reconstitution is altered by T cells in the graft and correlates with clinical outcomes after unrelated donor transplantation
.
Blood
.
2005
;
106
(
13
):
4370
-
4376
.
3.
Ruggeri
L
,
Capanni
M
,
Urbani
E
, et al
.
Effectiveness of donor natural killer cell alloreactivity in mismatched hematopoietic transplants
.
Science
.
2002
;
295
(
5562
):
2097
-
2100
.
4.
Davies
SM
,
Ruggieri
L
,
DeFor
T
, et al
.
Evaluation of KIR ligand incompatibility in mismatched unrelated donor hematopoietic transplants. Killer immunoglobulin-like receptor
.
Blood
.
2002
;
100
(
10
):
3825
-
3827
.
5.
Lanier
LL
,
Corliss
B
,
Phillips
JH
.
Arousal and inhibition of human NK cells
.
Immunol Rev
.
1997
;
155
(
1
):
145
-
154
.
6.
Yawata
M
,
Yawata
N
,
Draghi
M
,
Little
AM
,
Partheniou
F
,
Parham
P
.
Roles for HLA and KIR polymorphisms in natural killer cell repertoire selection and modulation of effector function
.
J Exp Med
.
2006
;
203
(
3
):
633
-
645
.
7.
Ruggeri
L
,
Mancusi
A
,
Capanni
M
, et al
.
Donor natural killer cell allorecognition of missing self in haploidentical hematopoietic transplantation for acute myeloid leukemia: challenging its predictive value
.
Blood
.
2007
;
110
(
1
):
433
-
440
.
8.
Cooley
S
,
Trachtenberg
E
,
Bergemann
TL
, et al
.
Donors with group B KIR haplotypes improve relapse-free survival after unrelated hematopoietic cell transplantation for acute myelogenous leukemia
.
Blood
.
2009
;
113
(
3
):
726
-
732
.
9.
Cooley
S
,
Weisdorf
DJ
,
Guethlein
LA
, et al
.
Donor selection for natural killer cell receptor genes leads to superior survival after unrelated transplantation for acute myelogenous leukemia
.
Blood
.
2010
;
116
(
14
):
2411
-
2419
.
10.
Cooley
S
,
Weisdorf
DJ
,
Guethlein
LA
, et al
.
Donor killer cell Ig-like receptor B haplotypes, recipient HLA-C1, and HLA-C mismatch enhance the clinical benefit of unrelated transplantation for acute myelogenous leukemia
.
J Immunol
.
2014
;
192
(
10
):
4592
-
4600
.
11.
Venstrom
JM
,
Dupont
B
,
Hsu
KC
, et al
.
Donor activating KIR2DS1 in leukemia
.
N Engl J Med
.
2014
;
371
(
21
):
2042
.
12.
Venstrom
JM
,
Pittari
G
,
Gooley
TA
, et al
.
HLA-C-dependent prevention of leukemia relapse by donor activating KIR2DS1
.
N Engl J Med
.
2012
;
367
(
9
):
805
-
816
.
13.
Weisdorf
D
,
Cooley
S
,
Wang
T
, et al;
participating center writing committee
.
participating center writing committee. KIR donor selection: feasibility in identifying better donors
.
Biol Blood Marrow Transplant
.
2019
;
25
(
1
):
e28
-
e32
.
14.
Howard
CA
,
Fernandez-Vina
MA
,
Appelbaum
FR
, et al
.
Recommendations for donor human leukocyte antigen assessment and matching for allogeneic stem cell transplantation: consensus opinion of the Blood and Marrow Transplant Clinical Trials Network (BMT CTN)
.
Biol Blood Marrow Transplant
.
2015
;
21
(
1
):
4
-
7
.
15.
Penack
O
,
Fischer
L
,
Gentilini
C
, et al
.
The type of ATG matters - natural killer cells are influenced differentially by thymoglobulin, lymphoglobulin and ATG-Fresenius
.
Transpl Immunol
.
2007
;
18
(
2
):
85
-
87
.
16.
Majhail
NS
,
Chitphakdithai
P
,
Logan
B
, et al
.
Significant improvement in survival after unrelated donor hematopoietic cell transplantation in the recent era
.
Biol Blood Marrow Transplant
.
2015
;
21
(
1
):
142
-
150
.
17.
Geethakumari
PK
,
Nair
RG
,
Grosso
R
,
Flomenberg
N
,
Grosso
D
.
Analysis of the impact of KIR B haplotype donors on outcomes after haploidentical (HI) and matched related (MR) hematopoietic stem cell transplantation (HSCT) [abstract]
.
Blood
.
2016
;
128
(
22
). Abstract
2991
.
18.
Sobecks
RM
,
Gallagher
MM
,
Askar
M
, et al
.
Influence of killer immunoglobulin-like receptor (KIR) and HLA genotypes on outcomes after reduced-intensity conditioning allogeneic hematopoietic stem cell transplantation for patients with AML and MDS: a report from the Center for International Blood and Marrow Transplant Research Immunobiology Working Committee [abstract]
.
Blood
.
2013
;
122
(
21
). Abstract
159
.
19.
Sobecks
RM
,
Wang
T
,
Askar
M
, et al
.
Impact of KIR and HLA genotypes on outcomes after reduced-intensity conditioning hematopoietic cell transplantation
.
Biol Blood Marrow Transplant
.
2015
;
21
(
9
):
1589
-
1596
.
20.
Hsu
KC
,
Keever-Taylor
CA
,
Wilton
A
, et al
.
Improved outcome in HLA-identical sibling hematopoietic stem-cell transplantation for acute myelogenous leukemia predicted by KIR and HLA genotypes
.
Blood
.
2005
;
105
(
12
):
4878
-
4884
.
21.
Oevermann
L
,
Michaelis
SU
,
Mezger
M
, et al
.
KIR B haplotype donors confer a reduced risk for relapse after haploidentical transplantation in children with ALL
.
Blood
.
2014
;
124
(
17
):
2744
-
2747
.
22.
Bachanova
V
,
Weisdorf
DJ
,
Wang
T
, et al
.
Donor KIR B genotype improves progression-free survival of non-Hodgkin lymphoma patients receiving unrelated donor transplantation
.
Biol Blood Marrow Transplant
.
2016
;
22
(
9
):
1602
-
1607
.
23.
Rocha
V
,
Ruggeri
A
,
Spellman
S
, et al;
Eurocord, Cord Blood Committee Cellular Therapy Immunobiology Working Party of the European Group for Blood and Marrow Transplantation, Netcord, and the Center for International Blood and Marrow Transplant Research
.
Killer cell immunoglobulin-like receptor-ligand matching and outcomes after unrelated cord blood transplantation in acute myeloid leukemia
.
Biol Blood Marrow Transplant
.
2016
;
22
(
7
):
1284
-
1289
.
24.
Hosokai
R
,
Masuko
M
,
Shibasaki
Y
,
Saitoh
A
,
Furukawa
T
,
Imai
C
.
Donor killer immunoglobulin-like receptor haplotype B/x induces severe acute graft-versus-host disease in the presence of human leukocyte antigen mismatch in T cell-replete hematopoietic cell transplantation
.
Biol Blood Marrow Transplant
.
2017
;
23
(
4
):
606
-
611
.
25.
Rashidi
A
,
Luo
X
,
Cooley
S
, et al
.
The association of CMV with NK-cell reconstitution depends on graft source: results from BMT CTN-0201 samples
.
Blood Adv
.
2019
;
3
(
16
):
2465
-
2469
.
26.
Solomon
SR
,
Aubrey
MT
,
Zhang
X
, et al
.
Selecting the best donor for haploidentical transplant: impact of HLA, killer cell immunoglobulin-like receptor genotyping, and other clinical variables
.
Biol Blood Marrow Transplant
.
2018
;
24
(
4
):
789
-
798
.
27.
Handgretinger
R
.
Donor selection for AML: do the KIR
.
Blood
.
2010
;
116
(
14
):
2407
-
2409
.

Author notes

The full-text version of this article contains a data supplement.

Supplemental data