Imatinib maintenance post-HSCT in Ph+ ALL

Results from a prospective, randomized trial evaluating prophylactic (n = 37) vs preemptive, measurable residual disease (MRD)-triggered imatinib (n = 38) maintenance following allogeneic hematopoietic stem cell transplantation (allo-HSCT) in adults with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) were published in Leukemia & Lymphoma by Pfeifer et al. The primary endpoint was molecular or hematologic relapse. 

Key data: At 8 years, no significant differences were observed between the prophylactic imatinib group and the MRD-triggered imatinib group for cumulative incidence of relapse (CIR; 14.5% vs 19.1%), leukemia-free survival (LFS; 63.7% vs 69.3%), overall survival (OS; 68.3% vs 70.9%), and non-relapse mortality (NRM; 7.9% vs 7.7%). Pre-transplant MRD levels ≥10⁻³ were predictive of higher CIR (47.5% vs 26.5%) and inferior LFS (45.0% vs 59.8%) compared with MRD levels above 10⁻⁴. Imatinib was well tolerated; the most common Grade 3/4 severe adverse events (SAEs) were gastrointestinal and pancytopenia, which were reported in nine and four patients, respectively. No imatinib-related deaths occurred.

Key learning: Prophylactic and MRD-triggered imatinib maintenance demonstrated equivalent long-term outcomes, supporting the use of either strategy in patients with Ph+ ALL after HSCT. Further investigation is required to determine the value of MRD levels in identifying patients at higher risk of relapse.