Sustained Superior Long-Term Outcomes and Cytogenetic Responses with Imatinib Mesylate in Chronic Phase Chronic Myeloid Leukaemia: Report from a Developing Country

Abstract

Imatinib mesylate is now a standard treatment for chronic myeloid leukaemia. Primary objective of our study was to report long-term survival outcomes in patients receiving Imatinib in chronic phase. Secondary objectives included determination of cytogenetic responses and toxicity profile of Imatinib mesylate. Three-hundred and four consecutive patients with chronic phase chronic myeloid leukaemia were evaluated between January 2001 to December 2007, for event-free survival, overall survival, complete cytogenetic response and toxicity profiles. Event-free and overall survivals were calculated by Kaplan-Meier estimates. Cox regression analysis was performed to evaluate the prognostic factors for survival. Univariate and multivariate analyses were performed for factors predictive of a complete cytogenetic response. Median follow-up was 48 months. Estimated 5-year event-free and overall survivals of all patients were 79% and 86%, respectively. On Cox regression analysis significant predictive factors for event-free survival were age < 50 years (P 0.002), complete cytogenetic response (P < 0.0001), low Sokal score (P 0.007), complete clinical (P < 0.0001) and haematological response (P < 0.0001). Complete cytogenetic response was achieved in 206 (67.8%) patients. On multivariate analysis, low Sokal score (P < 0.0001) and early chronic phase disease (P < 0.0001) emerged as the most significant predictors for achieving a complete cytogenetic response. An estimated 5.8% patients lost their complete cytogenetic response. Grade III/IV toxicity was observed in only 21 patients. Long-term treatment with Imatinib mesylate results in superior and durable responses in chronic phase chronic myeloid leukaemia. Our survival outcomes are similar to reported rates in the Western population.