A prophylactic tyrosine kinase inhibitor strategy based on measurable residual disease pre‐transplantation for Ph+ acute lymphoblastic leukemia undergoing allogeneic hematopoietic stem cell transplantation: A prospective multicenter cohort study

Abstract Relapse is the major cause of treatment failure in Philadelphia chromosome‐positive (Ph + ) acute lymphoblastic leukemia (ALL) undergoing allogeneic hematopoietic stem cell transplantation (allo‐HSCT). This study aimed to evaluate the effect of a prophylactic tyrosine kinase inhibitor (TKI) strategy on relapse in this population. Patients were assigned to prophylactic or control groups based on measurable residual disease (MRD) pre‐transplantation. The primary endpoint was the cumulative incidence of relapse. A total of 110 patients with Ph + ALL undergoing allo‐HSCT were enrolled in this prospective study. Thirty‐eight patients with positive MRD pre‐transplantation were included in the prophylactic group, and 72 with negative MRD pre‐transplantation were included in the control group. The 4‐year cumulative incidence of relapse was 25.3% (95% CI: 12.1%–41.0%) and 20.3% (11.6%–30.7%; HR = 1.272, 95% CI: 0.551–2.940, p = .549), and non‐relapse mortality was 10.5% (3.3%–22.7%) and 9.7% (4.2%–17.9%; HR = 1.094, 95% CI: 0.320–3.738, p = .928) in the prophylactic and control groups. The 4‐year overall survival was 71.8% (53.2%–84.1%) and 84.1% (72.9%–90.9%; HR = 1.746, 95% CI: 0.741–4.112, p = .196), and leukemia‐free survival was 64.1% (45.8%–77.7%) and 70.0% (57.6%–79.4%; HR = 1.212, 95% CI: 0.607–2.421, p = .585) in the prophylactic and control groups. Our results suggest that prophylactic TKI post‐HSCT in patients with positive MRD pre‐transplantation can produce outcomes comparable to negative MRD pre‐transplantation without TKI post‐HSCT.