An in vitro chemosensitivity test for the screening of anti-cancer drugs in childhood leukemia.

We applied the MTT dye reduction assay to the anti-cancer drug sensitivity test using short-term microplate cultures. Blast cells were cultured with approximately 25 anti-cancer drugs for 4 days. After cultivation, MTT dye was placed in each well, and the formazans generated by living cells were dissolved in acidified isopropyl alcohol. The absorbance of each well was measured at a scanning microplate photometer. When we made the table of the cytotoxicity index (CI) that was classified into anti-cancer drugs and concentrations for each leukemic sample, it was possible to compare efficacy with different drugs and to select the effective ones. Retrospectively, the in vitro results were compared with the clinical responses of the 34 patients (26 of acute lymphocytic leukemia [ALL] and eight of acute nonlymphoblastic leukemia [ANLL]) who were treated by combination chemotherapy. The following results were obtained: true-positive rate, 78.1%; true-negative rate, 57.1%; and predictive accuracy, 74.4%. Therefore, the MTT assay-CI table might serve as a reliable tool for the selection of effective chemotherapy in patients with acute leukemia.