Ph clone recurrence after imatinib discontinuation for chronic myelogenous leukemia patients who had complete molecular remission

「ABSTRACT」 Imatinib (IM) is a tyrosine kinase inhibitor that blocks the kinase activity of BCR-ABL fusion protein, thereby inhibiting Ph-positive leukemic progenitor cell proliferation. Imatinib has produced excellent clinical and cytogenetic/molecular responses against chronic myelogeneous leukemia (CML), and is now the first-line treatment of CML. A few to 34% of patients reaches a complete molecular response (CMR) by IM treatment, however it is not known whether patients who have a CMR require continued therapy to maintain it or whether IM can safely be discontinued. We analyzed the cytogenetic and molecular outcomes of 7 patients with CML, for whom IM therapy had been discontinued after a CMR. From January 2002 to September 2006, 16 patients reached CMR by IM therapy at our institute. Because of economic reasons or adverse events, 7 of the 16 patients had IM discontinued and all had an early relapse. The median time to relapse was 4.9 months (range, 2-6 months). One factor for relapse was that the duration of molecular remission before IM was discontinued was short (4.3 months; range, 1-12 months). Based on these results, discontinuation of IM therapy for patients who have a CMR can not be recommended. More information about cases of Japanese CML must be gathered in order to devise effective CML treatment strategies for patients who achieved a CMR.