Imatinib Mesylate in the Treatment of Relapse of Chronic Myeloid Leukemia after Allogeneic Stem Sell Transplantation.

Objective: To determine whether imatinib mesylate is effective against chronic myeloid leukemia (CML) that relapses as CML in chronic phase following allogeneic stem cell transplantation (allo-HSCT).

Methods: We studied 5 patients treated with imatinib mesylate for recurrent CML after allo-HSCT. 2 patients relapsed as CML in chronic phase with hematological evidence of relapse, and one of whom was refractory to donor lymphocyte infusion (DLI). The remaining 3 patients relapsed as CML in chronic phase with cytogenetic evidence of relapse. The patients were followed for hematological and cytogenetic response.

Results: all of 5 patients achieved hematological and cytogenetic response within 5 months.The 2 patients with hematological evidence of relapse and minimal level of donor chimerism experienced severe pancytopenia, followed shortly by a hematological recovery, disappearance of BCR-ABL fusion gene positive cells, and conversion of complete donor chimerism. In 3 patients, a hematological and cytogenetic response was associated with chronic graft-versus-host disease. With a median follow-up of 36 (12~46) months, after cessation of imatinib mesylate, all patients are alive and remain in complete cytogenetic remission.

Conclusion: We have shown that patients who relapsed as CML in chronic phase after allo-HSCT showed very good therapeutic responses to imatinib mesylate, which were rapid, durable, with conversion to full donor chimerism and complete disappearance of BCR-ABL fusion gene positive cells, in spite of a prolonged relapse, an apparent loss of donor chimerism, and a failed prior response to DLI.