Prognostic Factors Associated with a Stable MR4.5 Achievement in Chronic Myeloid Leukemia Patients Treated with Imatinib

Deep molecular response in chronic myeloid leukemia (CML) patients treated with imatinib is a prerequisite for possible discontinuation. We identify clinico-biologic features linked with the probability of reaching MR4.5 (BCR-ABL/ABL ≤ 0.0032% IS) as a stable response (confirmed on two or more consecutive determinations). In a series of 208 patients treated with imatinib first-line outside clinical trials, after a median follow-up of 7 years the incidence of stable MR4.5 was 34.6%, obtained in median time of 5.4 years. In univariate analysis, female gender (p = 0.02), lower median age (56.4 vs 58.6, p = 0.03), Sokal risk stratification (p = 0.01) and e14a2 type of transcript (43% vs 31%, p = 0.02) are associated to achievement of a stable MR4.5. In multivariate regression analysis, female gender (HR 1.6, 95% CI: 1.1-2.6; P = 0.022), Sokal risk (HR 1.4, 95% CI: 1.1-2.3; p = 0.03), type of transcript (e14a2 vs e13a2 type, HR 1.6, 95% CI: 1.3-2.9; P = 0.03) and achievement of an early molecular response (EMR) at 3 months (HR 1.5, 95% CI: 1.2-2.8; P = 0.01), retained statistical significance. These clinical and biologic features associated with the achievement of a stable deep molecular response should be taken into account at a time when treatment-free remission strategies are being actively pursued in the management of CML.