Prediction of chemotherapy response in human leukemia using an in vitro chemotherapy sensitivity test on the leukemic...

An in vitro test system to quantitatively assess the chemotherapy sensitivity of human acute leukemic colony-forming cells (L-CFU) in relation to normal granulocytic precursor cells (CFU-C) has been developed. After simultaneous exposure of leukemic and normal bone marrow cells to individual drugs in vitro, cells were grown using an improved agar culture method with daily feeding. A sensitivity index (SI) was determined as the ratio of survival fraction of CFU-C to that of L-CFU, L-CFU being more (or less) sensitive than CFU-C if the SI were higher (or lower) than unity. Thirty SI were determined for 6 single drugs actually given in various combinations to a total of 9 patients (8 with acute nonlymphocytic leukemia and 1 with chronic myelomonocytic leukemia). A highly significant correlation was observed between high (or low) SI and achievement of (or failure to achieve) complete remission, with only 6 false correlations (p = 0.0013). Also, the mean of these SI (MSI) for the multiple single drugs given to each patient as components of a combination chemotherapy was used to indicate an overall sensitivity for each trial of the chemotherapy. Among the 10 chemotherapy trials (1 trial each for 8 patients and 2 trials for 1 patient), 4 trials resulting in complete remission had MSI higher than 1.0, and 6 trials not resulting in complete remission had MSI lower than 1.0 (p = 0.0048). This assay system appears useful in predicting the response of patients to chemotherapy and in the selection of the most effective drugs for use in individual patients.