Objective: We investigated whether minimal residual disease (MRD) status in adult patients with Philadelphia chromosome (Ph)-negative acute lymphoblastic leukemia (ALL) is useful for decision on clinical indications for allogeneic hematopoietic stem cell transplantation (HSCT). Methods: We prospectively monitored MRD after induction and consolidation therapy in adult patients with Ph-negative ALL. Results: Among 103 adult ALL patients enrolled, 59 were Ph-negative, and MRD status was assessed in 51 patients. The probability of 3-year overall survival (OS) and disease-free survival (DFS) was 69% (95%CI 54-80) and 50% (95%CI 36-63), respectively. Patients who were MRD-negative after induction therapy (n = 15) had a significantly better 3-year DFS compared with those who were MRD-positive (n = 30; 73% vs 41%, P = 0.018). Patients who were MRD-positive after induction but became MRD-negative after consolidation chemotherapy C in the first course (n = 11) showed a significantly worse 3-year DFS compared with patients who were MRD-negative after induction chemotherapy A in the first course (45% vs 73%, P = 0.025). Conclusions: These results indicate that DFS of about 70% can be expected in MRD-negative patients after induction therapy, and the patients did not benefit from HSCT in 1CR. This study was registered with the UMIN Clinical Trials Registry (UMIN-CTR), number UMIN000001519.
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