Observation on frequency & clinico-pathological significance of various cytogenetic risk groups in multiple myeloma: an experience from India

BACKGROUND & OBJECTIVES Multiple myeloma (MM) is a plasma cell malignancy characterized by cytogenetic heterogeneity. In comparison with conventional karyotyping, fluorescence in situ hybridization (FISH) can efficiently detect various genetic changes in non-cycling plasma cells in 50-90 per cent of MM cases. The present study was undertaken in MM patients to evaluate the frequency and clinico-pathological significance of various cytogenetic abnormalities in the Indian population. METHODS Interphase FISH was applied on purified plasma cells of 475 patients with MM using specific probes. Interphase FISH for 1q gain/1q amplification was performed on a separate group of 250 newly diagnosed MM patients. RESULTS Low frequency of Δ13 [-13/del(13q)] (32%) and t(11;14) (5%) was observed in our 475 patients probably due to ethnic diversity. Clustering of Δ13, del(17)(p13.1) and IgH translocations in non-hyperdiploidy confirmed prognostic significance of ploidy in MM. t(4;14) and del(17)(p13.1) were high-risk groups due to correlation with high serum β2-microglobulin, increased plasma cells and advanced disease. Hyperdiploidy and t(14;16) were associated with higher age group. In a separate group of 250 patients, 1q amplification [amp(1q)] in combination with Δ13 and/or del(17p) with t(4;14) revealed association with adverse clinico-laboratory features, which confirmed progressive role of amp(1q) with adverse prognostic impact. Amp(1q) was clustered at 1q21 and 1q25 loci. INTERPRETATION & CONCLUSIONS Based on our findings, it appears that comprehensive analysis of various cytogenetic aberrations by interphase FISH is a powerful strategy being adapted for risk stratification of MM.