FISH ANALYSIS FOR CML MONITORING

Conventional cytogenetics is considered the gold standard for evaluati ng CML during interferon (IFN) treatment. Drawbacks to this approach a re the small number of metaphases available during IFN therapy and the impossibility of scoring interphase cells. We applied, besides cytoge netics, double-color FISH (dc-FISH) detection of BCR-ABL gene fusion t o monitor 20 CML patients on IFN. dc-FISH easily detected 200 cells pe r specimen, while with cytogenetic examination a mean of 16.1 mitoses per sample were scored. Though the correlation of dc-FISH and cytogene tic data was good (r = 0.77, p < 0.001), the discrepancy between the t wo methods as regards the proportion of leukemic cells in the marrow w as often important. dc-FISH detected a relevant proportion of BCR-ABL cells in three patients classified as complete cytogenetic responders and showed that, after 9-12 months of IFN treatment, a significant re duction of BCR-ABL+ cells was present in all the 20 patients tested. T his might suggest that all CML patients are potentially responsive to IFN. Though more data are required, we think that dc-FISH is more info rmative than cytogenetic analysis for CML monitoring. Notably because of the simplicity of the procedure, this method could be easily standa rdized among different laboratories, thus permitting cross-comparison in therapeutic trials.