Results of a multicenter phase II trial for older patients with c‐Kit‐positive acute myeloid leukemia (AML) and high‐risk myelodysplastic syndrome (HR‐MDS) using low‐dose Ara‐C and Imatinib

Abstract

BACKGROUND. Imatinib (IM) is a potent tyrosine kinase inhibitor of c‐Kit. c‐Kit is expressed in the majority of patients with acute myeloid leukemia (AML). Whereas clinical trials evaluating monotherapy with IM in AML revealed low response rates, Ara‐C and IM showed synergistic effects in vitro. This suggested evaluation of a combination treatment. METHODS. Low‐dose Ara‐C (LDAC) combined with IM was tested to determine the efficacy and safety of this regimen. Forty patients from 4 centers with c‐Kit‐positive AML (n = 34) and high‐risk myelodysplastic syndrome (HR‐MDS) (n = 6) with a median age of 73 years were enrolled. They were either not eligible for myelosuppressive therapy and/or had recurring/refractory disease. RESULTS. Thirty‐eight patients were evaluable for analysis. In 6 of 38 patients a blast response was observed. Eight of 38 patients showed stable disease for more than 2 months. The objective hematologic response rate was low (11%), with 2 patients showing hematologic improvement and 1 each with a partial response (PR) or complete response (CR). Median overall survival was 138 days, with 20% of patients alive after an observation period of 600 days. Study medication was applied in an ambulatory setting with minimal hospitalization time, an early mortality rate of only 18.9%, and a low toxicity rate. CONCLUSIONS. LDAC plus IM does not appear to be inferior in older AML patients incomparison with historic controls receiving myelosuppressive therapy. However, this trial also shows that LDAC/IM does not appear to be more effective than LDAC monotherapy in a patient population not selected for appropriate molecular markers. Cancer 2007 © 2007 American Cancer Society.