Adriamycin and cytosine arabinoside contribute equally to prediction of response in acute myelocytic leukemia with improved confidence level.

Samples from 15 patients with acute myeloid leukemia (AML) were studied in a colony-inhibition assay of drug sensitivity. In vitro sensitivity to both Adriamycin (Adr) (1-h incubation) and cytosine arabinoside (AraC) (24-h and continuous incubation) were determined, as were the tritiated thymidine suicide indices (SI) during the 24-h incubation with AraC. The sensitivity of the proportion of cells entering S-phase during the 24-h incubation was also evaluated. Using discriminant analysis a function was derived to separate the patients into two groups, those who failed remission induction therapy, or nonresponders (group 1), and those who entered complete remission (group 2). The only variables that contributed to prediction were the Adr (1 h) and Ara-C (24 h) results. Overall, 87% (13/15) of the patients were correctly grouped using this function, with a confidence level for nine of these 13 patients of greater than 80%. Adr and AraC results contributed equally to the prediction.