Evaluation of minimal residual disease in patients with chronic myeloid leukaemia on IFN-alpha 2b therapy using conventional cytogenetics and fluorescence in situ hybridization.

ABSTRACT

BACKGROUND: Chronic myeloid leukaemia (CML) is a haematopoietic malignancy characterized by the presence of the Philadelphia (Ph) chromosome that results from balanced reciprocal translocation between chromosomes 9 and 22 leading to the formation of the bcr/abl fusion gene. Studies have shown that interferon-alpha (IFN-alpha) therapy induces both cytogenetic (reduction in Ph+ cells) and molecular response (reduction in the bcr/abl positive cells) in a large proportion of patients, thereby improving their prognosis and survival. There are no reports available from India on the clinical management of CML patients using IFN-alpha therapy and molecular methods for the evaluation of residual disease. We evaluated the efficacy of IFN-alpha 2b therapy bysequential cytogenetic and molecularanalysis. METHODS: Karyotypingwas done from G-banded metaphases obtained from 24-hour culture of bone marrow aspirates of 45 patients. Cytogenetic analysis was repeated at intervals of 4-6 months during the course of IFN-alpha therapy. Dual-colour fluorescence in situ hybridization (FISH) analysis using specific probes for bcr and abl genes was done to assess the molecular response. RESULTS: Eight patients achieved complete cytogenetic response with no Ph+ cells. Using FISH analysis, 4 of these patients were negative for the fusion gene implying a complete response, while the remaining 4 patients showed bcr/abl fusion signals that represent residual disease. CONCLUSION: Our study emphasizes the need for sequential cytogenetic and molecular analysis in the management of patients with CML and for the evaluation of minimal residual disease in patients on IFN-alpha therapy.