PREDICTION OF POST-TRANSPLANT RELAPSE IN THE MYELODYSPLASTIC SYNDROMES VIA EVALUATION OF STEM CELLS

Abstract

Introduction: Allogeneic stem cell transplant (alloSCT) remains the only curative treatment for the myelodysplastic syndromes (MDS), but relapse is common. Studies using error-corrected sequencing (ECS) on bulk bone marrow (BM) have shown that molecular residual disease is predictive of relapse. But the sensitivity of this approach is limited, and it is not known what cells give rise to relapse. Methods: To test our hypothesis that hematopoietic stem cells (HSCs) drive post-transplant relapse, we developed a protocol to perform ECS on as few as <25 HSCs. We used this new tool to ask if post-transplant relapse originates from MDS HSCs, and whether their persistence predicts for relapse. We also sought to determine if curing MDS requires eradication of MDS HSCs, or whether they are simply suppressed by graft-versus-tumor effect. Results: We sequenced HSCs, multipotent progenitors (MPPs), restricted progenitors, and bulk BM from 33 MDS patients who underwent alloSCT (with an additional 20 specimens to be presented). Persistence of mutations in HSCs/MPPs in the first 120 days post-transplant was 100% specific and 84% sensitive for relapse, while detection of mutations in bulk BM was only 41% sensitive and 85% specific (Figure). Average time from mutation detection in HSCs/MPPs to relapse was 6.9 months. Conclusions: In conclusion, we have shown for the first time that relapse of MDS after allogeneic transplant is driven by failure to eradicate MDS HSCs, and that detection of MDS HSCs early after transplant is highly predictive for relapse. This can identify patients who may benefit from early post-transplant interventions to forestall relapse.