Multi-center analysis of the effect of T-cell acute lymphoblastic leukemia subtype and minimal residual disease on allogeneic stem cell transplantation outcomes

This study aims to provide a detailed analysis of allogeneic stem cell transplantation (allo-SCT) outcomes in a large T-cell acute lymphoblastic leukemia (T-ALL) cohort with a specific emphasis on the effects of pre-transplant minimal residual disease (MRD) and disease subtype, including the aggressive early-thymic precursor (ETP) subtype. Data from 102 allo-SCT patients with a diagnosis of T-ALL from three centers were retrospectively analyzed. Patients were grouped into four T-ALL subtypes: ETP, early, cortical and mature. At 3 years, overall survival (OS), PFS, non-relapse mortality and cumulative incidence (CI) progression were 35, 33, 11 and 55%, respectively. Patients transplanted in first complete remission (CR1) had a 3-year OS of 62% versus those transplanted in CR2 or greater (24%) (hazards ratio 1.6, P=0.2). Patients with MRD positivity at the time of transplant had significantly higher rates of progression compared with those with MRD negativity (76 vs 34%, hazards ratio 2.8, P=0.006). There was no difference in OS, PFS or cumulative incidence (CI) progression between disease subtypes, including ETP (n=16). ETP patients transplanted in CR1 (n=10) had OS of 47%, comparable to other disease subtypes, suggesting that allo-SCT can overcome the poor prognosis associated with ETP. MRD status at transplant was highly predictive of disease relapse, suggesting novel therapies are necessary to improve transplant outcomes.