Intensity of Induction Regimen and Outcomes Among Adults with Ph plus ALL Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

Tyrosine kinase inhibitors (TKIs) are essential for the treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) and have allowed for effective, low intensity induction regimens including no or minimal chemotherapy. Whether the use of low intensity induction regimens impacts outcomes after allo-geneic hematopoietic stem cell transplant (alloHCT) is less understood. We identified consecutive adult patients with Ph+ ALL undergoing alloHCT in first complete remission (CR1) at our center from 2010 to 2021 and examined the impact of pre-transplant induction intensity on outcomes. Among the 87 identified patients, 44 (51%) received low intensity induction and 43 (49%) received induction with high intensity chemotherapy. Patients receiving low intensity induction were older (median age 60 vs. 47 years, p < 0.01). Following in-duction, measurable residual disease (MRD) negativity by BCR::ABL1 RT-PCR was similar in the low and high intensity induction cohorts (54% and 52% respectively). Receipt of reduced intensity transplant conditioning was not associated with intensity of induction regimen (39% vs. 19% in low vs. high, respectively, p = 0.06). At a median follow-up of 21 months from transplant, there was no difference between low and high intensity in-duction with respect to 2-year disease-free survival (58% vs. 56%), 2-year overall survival (62% vs. 63%), 2-year cumulative incidence of relapse (9% vs. 17%), and 2-year non-relapse mortality (33% vs. 29%). We also found no difference in outcomes when patients were segmented by both induction and conditioning regimen intensities. Our retrospective analysis suggests that induction intensity does not impact post-transplant outcomes among patients with Ph+ ALL transplanted in CR1.