Prognostic value of in vitro uptake and retention of cytosine arabinoside in acute myelogenous leukemia.

In vitro uptake and retention of 3H-cytosine arabinoside (ara-C) was studied in 68 acute myelogenous leukemia (AML) patients (ten were studied twice) treated with a regimen containing conventional (54 patients) or high doses (24) of ara-C. Drug uptake and retention after four hours were measured following 30 minutes exposure to 1 and 50 micrograms/mL of ara-C. A good correlation was observed between high uptake in the acid soluble (AS) fraction (P less than .01), or high retention in the acid insoluble (Al) fraction (P less than .03) of 1 microgram, but not 50 micrograms, of the drug and obtainment of complete remission (CR) in patients treated with conventional doses of ara-C. Patients with a high percentage of ara-C retained in the AS fraction (greater than 26%) have a significantly longer CR duration than patients with a lower level of retention (P less than .02). In 17 patients who achieved a CR in spite of a low tritiated ara-C uptake, the clonogenic leukemic (CFU-L) cells were especially sensitive to drugs (15 of 17 v three of 11 among resisting patients).