In vitro drug sensitivity studies of CFUc in chronic myelocytic leukemia: I. Suicide indices and busulfan sensitivity determinations during the chronic phase.

Serial clonogenicity studies employing an agar CFUc culture assay are being performed on cells from CML patients to determine if clonal growth, 3HTdR suicide indices (SI) and in vitro busulfan sensitivity are of prognostic significance in predicting blastic transformation. Initial studies performed on specimens obtained from 20 chronic phase patients were directed at determining whether blood and marrow cells differed in growth pattern, SI, and busulfan sensitivity and whether the cells giving rise to clusters differed from those forming colonies. In comparing marrow to blood cells, there was a correlation between the two with respect to the number of colonies produced and the sensitivity of the clonogenic cells to busulfan. By contrast the SI of blood and marrow clonogenic cells were not correlated. In both blood and marrow, colony forming cells had a higher SI and were more sensitive to busulfan than were cluster forming cells.