Early Intervention in Minimal Residual Disease after Allogeneic Transplant for Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia: Prolonged Survival by Imatinib.

Minimal residual disease (MRD) was examined using quantitative polymerase chain reaction in 34 patients with Philadelphia chromosome- positive acute lymphoblastic leukemia (Ph⁺ ALL) who received allogeneic hematopoietic stem cell transplantation (HSCT). Patients were divided into two groups according to the time of transplant (Group A; n=17, – 2000 and Group B; n=17, 2001-). Group B had a significantly higher overall survival rate than Group B (74.2% vs 29.4%, P<0.01). In Group A, MRD+ after HSCT indicated imminent hematological relapse with subsequent death. On the contrary, in Group B, 8 patients showed MRD after HSCT. However, only one died of leukemia during the observation. Among the MRD+ patients after HSCT, the probability of hematological relapse was higher in group A than in group B (100% vs 20%, P<0.05). MRD-based clinical interventions such as Imatinib administration, donor lymphocyte infusion, or second HSCT may contribute to longer survival. In particular, imatinib introduce MRD-negativity in most patients, resulting better performance status and time for preparing next strategies. Two patients who became MRD-negative after imatinib treatment developed molecular relapse after imatinib discontinuation. Thus, Imatinib may contribute to the improvement of overall survival, however, an allogeneic power may be required for the cure of leukemia.