SINGLE-CELL SUSPENSION ASSAY WITH AN MTT END-POINT IS USEFUL FOR EVALUATING THE OPTIMAL ADJUVANT CHEMOTHERAPY FOR ADVANCED GASTRIC-CANCER

One hundred and forty-eight patients with gastric cancer admitted to K eio University Hospital between July 1988 and October 1992 underwent r esection of the primary lesion, as well as single-cell suspension assa y of fresh surgical materials with (4,5-dimethylthiazol-2-yl)-2,5-diph enyltetrazolium bromide (MTT assay) for chemosensitivity evaluation. F ifty patients with histologically stage III or IV gastric cancer were enrolled in this study, among whom 10 received no chemotherapy after s urgery while 40 received chemotherapy at equivalent dose levels after surgery. The patients given chemotherapy were divided into two groups consisting of an ''Adapted''' group treated with at least one agent id entified as effective by the assay, and a ''Non-adapted'' group treate d with agents to which the cells were not sensitive in the assay, in o rder to identify the optimal cut-off inhibition rate (IR) in MTT assay for evaluation of the appropriate adjuvant cancer chemotherapy after surgery. A cut off IR of 30% was optimal for differentiating the survi val rates between the ''Adapted''' and ''Non-adapted'' groups. Patient s treated with drugs which showed more than 30% IR on their surgical s pecimens showed a better survival rate than patients treated with drug s which were ineffective in the assay.