Long-Term Pre-Transplant Imatinib Can Improve the Outcome of Non-Myeloablative Stem Cell Transplantation without Increasing the Morbidity in Ph+ Chronic Myeloid Leukemia.

Background and Objectives: Although non-myeloablative preparative regimens are being increasingly used due to its reduced toxicity associated with allogeneic transplantation, post-transplant relapses are still problematic. The use of imatinib prior to transplant may potentially allow disease control before SCT and accordingly induce the better transplant outcome in CML patients.

Patients and Methods: The role of imatinib before a non-myeloablative stem cell transplantation (NST) was examined in 25 CML patients. Imatinib was pretreated for median 10.8 months. There were 13 men and 12 women with a median age of 35 (19 – 53) years. Of these, 15 patients were in accelerated phase (AP), and rest of them in chronic phase (CP) at the time of diagnosis.

Results: At the time of transplant, all but 1 patient were in complete cytogenetic response and 4 of them were in molecular remission. Normalized BCR-ABL transcript level decreased from 0.65 to 0.00163 during imatinib therapy. All the patients received fludarabine-based regimens. With a median follow-up of 6.9 months (range, 1.3 – 43 months), all the patients are alive and transplant-related mortality was not observed. After transplantation, 4 CP and 7 AP patients additionally achieved molecular remission. Acute graft versus host disease (GVHD) was observed in 4 (16%) of 25 patients, meanwhile chronic GVHD was observed in 10 (59%) of 17 evaluable patients.

Conclusions: This study suggests that the use of imatinib followed by NST can offer an advantage of reduced relapse without increased toxicity. Prospective randomized trial with a larger number of patients is remained to clarify these clinical observations.