Abstract

Background: Recent studies revealed that Nucleophosmin1 mutated (NPM1mut) based minimal residual disease (MRD) monitoring allows identification of patients (pts) with acute myeloid leukemia (AML) at high risk of relapse. NPM1mut MRD monitoring remains of clinical relevance even in the context of concurrent gene mutations, e.g . FLT3 internal tandem duplications (FLT3- ITDpos) and DNA methyltransferase 3 (DNMT3Amut). However, data are varying with regard to the type of material that was used (bone marrow, BM; peripheral blood, PB) and the clinically relevant time points of MRD assessment.

Aims: To confirm our previous results on the clinical relevance of NPM1mut transcript levels (TL) in an extended cohort of 611 younger AML pts [18 to 60 years (yrs)] harboring NPM1mut.

Methods: All 611 pts were enrolled in one of four AMLSG [AMLHD98A (n=46; NCT00146120); AMLSG 07-04 (n=199; NCT00151242); AMLSG 09-09 (n=256; NCT00893399); AMLSG 16-10 (n=110; NCT01477606)] treatment trials. Treatment comprised two cycles of induction therapy (idarubicin, cytarabine, etoposide) with or without ATRA or gemtuzumab ozogamicin, or 1 cycle of daunorubicin and cytarabine followed by 1 to 4 cycles of high-dose cytarabine (n=363, 59%), autologous (n=19, 3%) or allogeneic stem cell transplantation (n=162, 27%). 67 (11%) pts did not receive or complete post-remission therapy. NPM1mut TL (ratio of NPM1mut/ ABL1 transcripts x 104) were determined by RQ-PCR; the sensitivity of the assays was 10-5 to 10-6. Median follow-up (FU) for all patients: 3.2 yrs.

Results: A total of 3527 BM and 2812 PB samples from 611 NPM1mut pts were analyzed at diagnosis [n=532 (BM); n=385 (PB)], after each treatment cycle [n=1790 (BM); n=1264 (PB)] and during FU [n=1205 (BM); n=1163 (PB)]. Pretreatment NPM1mut TL in BM and PB were not associated with clinical characteristics or AML-associated gene mutations and had no impact on relapse-free and overall survival (OS). Cox regression analysis using NPM1mut TL in BM and PB as continuous variable at different time points during therapy was significantly associated with shorter remission duration (RD) and OS.

After twotreatment cycles a > 2log reduction of NPM1mut TL in BM and PB was significantly associated with a superior OS [p<.0001 (BM); p<.0001 (PB)] and a lower cumulative incidence of relapse (CIR) [p=.0002 (BM); p=.02 (PB)]. At this time point 63/395 (16%) pts became RQ-PCR negative (RQ-PCRneg) in the BM. CIR at 4 yrs was 10% for RQ-PCRneg pts versus 40% for RQ-PCR positive (RQ-PCRpos) pts (p<.0001) and 4-yrs OS was 82% vs 63%, respectively; (p=.01). With regard to PB 129/293 (44%) pts became RQ-PCRneg which was also associated with a lower CIR (17% vs 49%, p<.0001) but not with a difference in OS (p=.07). Multivariable analysis revealed RQ-PCRneg in the BM as an independent factor for better OS (p=.02) and longer RD (p=.001), whereas in PB RQ-PCRneg was only significant for the endpoint RD (p<.0001). In explorative subgroup analyses achievement of RQ-PCRneg in the BM was significantly associated with a lower CIR independent of the FLT3 -ITD (p=.006) and DNMT3A (p=.04) mutation status. Achievement of RQ-PCRneg in BM was significantly superior in the FLT3 -ITDwildtype / DNMT3Awildtype (26%) and the FLT3 -ITDpos/ DNMT3Awildtype (25%) genotypes compared to the FLT3 -ITDpos/ DNMT3Amut (8%) and FLT3 -ITDwildtype/ DNMT3Amut (8%) genotypes (p <.001).

At the end of treatment, 129/284 pts (45%) were RQ-PCRneg in the BM. CIR was 22% for RQ-PCRneg pts versus 48% for RQ-PCRpos pts (p<.0001). Again, this translated into a better OS (73% vs 61%, respectively; p=.01). Multivariable analysis revealed RQ-PCRneg in the BM and PB as an independent factor for better OS [p=.05 (BM); p<.0001(PB)] and longer RD [p<.0001 (BM); p<.0001(PB)]. During FU, the CIR at 4 yrs for pts exceeding our previously defined cut-off value of >200 NPM1mut TL was 88% in each BM and PB with a median time to relapse of only 1.7 and 1.6 months, respectively.

Conclusions: In our study NPM1mut MRD assessment in BM after 2 treatment cycles was highly informative to identify pts at an increased risk of relapse. Attainment of RQ-PCRneg was significantly associated with a lower CIR and a better OS, independent of concurrent FLT3 -ITD and DNMT3A mutation . However,achievement of RQ-PCRneg strongly correlated with FLT3 -ITDpos/ DNMT3Amut and FLT3 -ITDwildtype/ DNMT3Amut genotypes. During FU, TL above >200 were highly predictive for relapse in both BM and PB samples.

Disclosures

Fiedler: Amgen: Patents & Royalties; Amgen, Gilead, GSO, Teva, Jazz Pharmaceuticals: Other: Support for meeting attendance; Amgen, ARIAD/Incyte: Membership on an entity's Board of Directors or advisory committees; Amgen, Pfizer: Research Funding. Kindler: Novartis: Membership on an entity's Board of Directors or advisory committees. Götze: Celgene: Honoraria; Novartis: Honoraria; Amgen: Honoraria; Abbvie: Honoraria; BMS: Honoraria. Schroeder: Celgene: Consultancy, Honoraria, Other: travel support. Salwender: Amgen: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Honoraria and travel support: Janssen Cilag, Celgene, BMS.: Honoraria, Other: Travel support; Takeda: Honoraria. Döhner: Abbvie: Honoraria; Sunesis: Honoraria; Arog Pharmaceuticals: Honoraria, Research Funding; Seattle Genetics: Honoraria; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Agios: Honoraria; Astex Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer Ingelheim: Research Funding; Bristol Myers Squibb: Research Funding; Celator: Honoraria; Pfizer: Research Funding; Amgen: Honoraria; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Author notes

*

Asterisk with author names denotes non-ASH members.