Role of the MTT chemosensitivity test in the prognosis of gastric cancer patients after postoperative adjuvant chemotherapy

The clinical usefulness of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) chemosensitivity test (MTT assay; MTTA) in the selection of anticancer drugs against advanced gastric cancer (AGC) was evaluated. MTTA is widely used to predict patient responses to particular drugs, allowing for the selection of appropriate chemotherapeutic drugs and the avoidance of ineffective chemotherapeutic drugs, thereby improving patient survival. Since 1989, we have accumulated MTTA efficacy data from AGC patients. In this study, the present clinical roles of MTTA and the data from 202 patients with stage III or IV gastric cancer analyzed for survival outcome following surgery, with or without postoperative chemotherapy, evaluated by MTTA, are discussed. The patients were divided into 3 groups; an adapted group found to be sensitive to chemotherapy by MTTA, a non-adapted group found to be insensitive to chemotherapy by MTTA and a group that received no chemotherapy. For stage III gastric cancer patients, the adapted group had a statistically better survival rate compared to the other groups, while for stage IV patients, there was no difference in survival rate between any of the groups. However, further classification of stage IV patients as to the presence or absence of peritoneal dissemination (P) showed that the adapted group with P showed better prognoses than the other groups with P. The analysis of data collected since 2000 revealed that the 11 patients in the taxane-adapted group, who received chemotherapeutic regimens that included taxanes and were found to be sensitive to taxanes by MTTA, demonstrated better survival than the taxane non-adapted group (n=11) (p=0.045). In conclusion, MTTA results predicted patient prognoses, based on the selection of appropriate chemotherapy.