Prediction of the response to chemotherapy in acute leukemia by a short‐term testin vitro

To detect sensitivity or resistance of leukemic cells to chemotherapy prior to treatment, a short‐term incubation method was employed. Blast cells from the peripheral blood or bone marrow of adult patients presenting with different forms of acute leukemia were analyzed for in vitro responsiveness to anticancer drugs in terms of suppression of ³H‐uridine incorporation into cellular nucleic acids. The following agents were tested over a wide range of concentrations: Adriamycin, cytosine arabinoside, thioguanine, 6‐mercaptopurine, prednisone, and 4‐hydroperoxycyclophosphamide. Retrospectively, the in vitro data were compared to the clinical response of the patients to polychemotherapy. In the majority of the patients, in vitro cytotoxic effectiveness of Adriamycin (doxorubicin) and cytosine arabinoside reflected the in vivo situation. The levels of in vitro inhibition that could distinguish between drug‐sensitive and drug‐resistant diseases appeared to be 30% for Adriamycin and 20% for cytosine arabinoside. No correlation was found between the Adriamycin effect in vitro and the proliferative state (rate of ³H‐thymidine incorporation) of the leukemic cell population. Serial in vitro sensitivity testing during the course of disease of various patients proved the ability of the test system to detect acquired resistance to chemotherapeutic agents. Therefore, the assay might serve as a reliable tool in the selection of effective chemotherapy in individual patients suffering from acute leukemia.