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

Abstract: Tyrosine kinase inhibitors are essential in treating Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph + ALL) and have allowed for effective, low intensity induction regimens. Whether the use of low intensity induction regimens impacts outcomes after allogeneic stem cell transplant (alloHSCT) is less understood. We identified consecutive adult patients with Ph + ALL undergoing alloHSCT in first complete remission (CR1) at our center from 2010 to 2021 and examined the impact of induction intensity on outcomes. Among the 87 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, p < 0.01). Following induction, measurable residual disease (MRD) negativity by BCR::ABL1 RT-PCR was similar in the low and high intensity cohorts (54% and 52% respectively). There was no difference between low and high intensity induction 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%). Outcomes were similar when patients were segmented by induction and conditioning regimen intensities. We demonstrate that induction intensity does not impact post-transplant outcomes among Ph + ALL patients Ph + ALL transplanted in CR1.