Durable molecular response to imatinib mesylate following nonmyeloablative allogeneic stem-cell transplantation for persisting myeloid blast crisis in chronic myeloid leukemia.

We report a chronic myeloid leukemia (CML) patient in chronic phase (CP) who developed blast crisis (BC) under imatinib mesylate administered in a dose reduced and non-continuous fashion because of hematologic intolerance. The patient underwent nonmyeloablative stem-cell transplant from a matched unrelated donor, but failed to achieve full donor chimerism and antileukemic response resulting in persistence of advanced disease. Complete hematologic, cytogenetic and molecular responses were attained 5 weeks after readministration of regularly dosed imatinib and two-step nested RT-PCR confirmed molecular remission throughout a 6 month follow-up period. This is the first case demonstrating that imatinib mesylate is a highly effective and safe treatment option to induce durable molecular remission in patients with CML who remain in myeloid blast crisis after nonmyeloablative allogeneic stem-cell transplantation.