RIC regimens are increasingly used for allo-SCT in older patients or patients with co-morbidities. The FB2 regimen (Fludarabine 120–150 mg/m2 + I.V. Busulfan 6.4 mg/Kg + ATG 5 mg/Kg) using PBSC as stem cell source is currently the most widely used RIC regimen in many European centres. On the other hand, in patients without a suitable HLA-matched donor, the use of umbilical cord blood stem cells for allo-SCT (uCBT) is increasingly considered, especially using the RIC regimen developed by the Minneapolis group. Series comparing PBSC vs CB as stem cells source for RIC allo-SCT are still scarce and using various RIC regimens before allo-SCT.
This retrospective single centre analysis compared two homogeneously treated cohorts of patients who had received between January 2007 and November 2010 in our department either a FB2/PBSC allo-SCT (n=52, males: 61%; median age: 59 years (range: 22–70)) or a FC-TBI/uCBT (Fludarabine 200 mg/m2 + Cyclophosphamide 50 mg/Kg + TBI 2 Grays regimen; n=39, males 49%; median age 56 years (range: 22–70). Except for age (p=0.03), there were no significant differences between the 2 groups regarding patients and diseases characteristics: gender (p=0.22), interval between diagnosis and transplant (PBSC: 9 months vs CB: 10 months, p=0.85), disease type (PBSC: myeloid disease 63% vs CB: 67%, p=0.75), status at transplant (complete remission PBSC: 77% vs CB: 67%, p=0.28), prior auto-SCT (PBSC: 35% vs CB: 33%, p=0.90). Donors in the PBSC group were as follows: sibling donors, n=30; HLA-MUD n=20, mismatched unrelated n=2. All patients from the CB group received 2 CB units (HLA matching 4/6 n=25; 5/6 n=53). As for GVHD prophylaxis, patients received cyclosporine (CsA) alone in case of an HLA-identical sibling donor, and CsA+ mycophenolate mofetyl in all other cases. None of the patients from the PBSC group received G-CSF after transplant, while it was administered to all CB recipients.
Median follow-up was respectively 19 and 20 months for the PBSC and the CB groups (p=NS). Engraftment and median time for neutrophils recovery were similar between the 2 groups: PBSC: 96% vs CB: 90%, p=0.22; and 17 days (range: 0–39) vs 16 days (range: 8–60), p=0.88, respectively. The median time for platelets recovery (>20000/mm3) was significantly higher in the CB group: 38 days (range: 13–150) vs PBSC: 0 days (range: 0–186) (p<0.0001). The cumulative incidences of grade II-IV and grade III-IV acute GVHD were comparable between both groups: PBSC: 31% and 15% vs CB: 26% and 8% (p=0.72 and p=0.28) as also the 2-years incidence of chronic GVHD: PBSC: 35% vs uCBT: 25%, p=0.54. 2-years NRM was significantly higher after uCBT: 26% vs 6%, p=0.02. Finally, there were no differences between the two groups in terms of 2-years OS, DFS and Relapse Incidence: PBSC: 62.3% vs CB: 60.8% (p=0.51); 58.7% vs 50.4% (p=0.43) and 36% vs 23% (p=0.31). In multivariate analysis, the source of stem cells (CB) remains associated with NRM (HR: 0.16, 95%CI: 0.05–0.5, p=0.001) but was not predictable for survivals.
Our study suggests that RIC uCBT is a valid alternative in patients lacking an HLA-matched related or unrelated donor and candidate for RIC allo-SCT. Prospective and randomized studies are warranted in order to establish the definitive role of uCBT, especially in patients with acute leukemia, where CB cells may offer a rapidly available source of stem cells in diseases with high tumor kinetics.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.