A Multicenter Analysis of Allogeneic Transplant Outcomes in Adults with Philadelphia-Like B-Cell Acute Lymphoblastic Leukemia in First Complete Remission.

Philadelphia-like acute lymphoblastic leukemia (Ph-like ALL) is a high-risk subset of B-cell ALL with a poor prognosis with conventional therapies. Diagnostic challenges and lack of standardized treatment protocols contribute to suboptimal outcomes. Additionally, while allogeneic hematopoietic cell transplantation (HCT) is frequently recommended in adults with Ph-like ALL given its high-risk nature, data supporting its role remains limited. We conducted a multicenter retrospective study evaluating outcomes of adult patients undergoing HCT in first complete remission (CR1) for Ph-like ALL compared to Philadelphia chromosome positive ALL (Ph-pos) and other B-cell Philadelphia negative (Ph-neg) ALL. Data was collected from five academic centers across the US, focusing on HCT outcomes for patients with ALL. Patients undergoing HCT in CR1 between 2006 and 2021 were included. Among 673 patients, 83 (12.3%) had Ph-like ALL, while 271 (40.3%) had Ph-pos and 319 (47.4%) had Ph-neg ALL. Outcomes following HCT in CR1 for Ph-like ALL were comparable to Ph-neg ALL, with no significant differences in 3-year overall survival (66% vs. 59%, P = .1), progression-free survival (59% and 54%, P = .1), or relapse rates (22% vs. 20%, P = .7). In contrast, Ph-pos ALL had superior outcomes; 3-year OS (75%, P < .001), PFS (70%, P = .001) and relapse (12%, P = .003), this is likely attributed to tyrosine kinase inhibitor therapy. Our study suggests that HCT, coupled with effective 2nd line therapies can possibly mitigate the poor prognosis associated with Ph-like ALL and offers promising outcomes for patients with Ph-like ALL.