Concept, Feasibility and Results of the Randomized Comparison of Imatinib Combination Therapies for Chronic Myeloid Leukemia: The German CML-Study IV

Targeted therapy with the BCR-ABL tyrosine kinase inhibitor imatinib induces high response rates in chronic myeloid leukemia (CML) patients (pts). Nevertheless, residual disease remains in virtually all pts on imatinib monotherapy as a potential cause of relapse. In July 2002, the German CML-Study Group activated the four-armed randomized controlled trial comparing imatinib 400mg/d with imatinib+IFN, imatinib+Ara-C, and imatinib after IFN failure in newly diagnosed pts with chronic phase CML. Randomization is stratified according to prognostic risk groups and not biased by consecutive allogeneic stem cell transplantation (SCT). High-risk pts are randomly assigned to primary imatinib-based therapies including a treatment arm with 800mg/d imatinib. By 7/05, 632 pts were randomized: imatinib 400mg/d (n=129), imatinib+IFN (n=179), imatinib+Ara-C (n=156), imatinib after IFN failure (n=157), and imatinib 800mg/d (n=11). According to the Hasford score, 35% of pts were low risk, 54% intermediate risk, and 11% high risk. At baseline, median WBC count was 67/nl (3–529), median platelet count 391/nl (34–2,799) and median hemoglobin 12.6 g/dl (6.1–16.6). We sought to evaluate results of pts with a >12 months follow-up (n=416), recruited between 7/02 and 6/04 (imatinib 400mg/d, n=102; imatinib+IFN, n=126; imatinib+Ara-C, n=104; imatinib after IFN failure, n=81; imatinib 800mg/d, n=3) and of pts with a >24 months follow-up (n=232), recruited between 7/02 and 6/03 (imatinib 400mg/d, n=55; imatinib+IFN, n=74; imatinib+Ara-C, n=54; imatinib after IFN failure, n=49) with respect to response, resistance, and progression. After 12 months of treatment cytogenetic data are available from 238/335 pts (71%) randomized to primary imatinib based therapies. 209 pts (63%) achieved a major cytogenetic remission (MCR; Ph+