[Evaluation of pre-operative administration of TS-1 in patients with advanced gastric or colorectal cancer--estimation of pathological effectiveness for postoperative adjuvant chemotherapy with TS-1].

: We performed surgical resections in 6 cases of advanced gastric cancer and 4 cases of colorectal cancer after preoperatively treating them with TS-1 at a daily dose of 80-100 mg/body for 2 weeks, and evaluated whether one can estimate their sensitivity to TS-1 by a pathological examination. Case 1 of type 3 advanced gastric cancer underwent surgery after one week interval following oral administration of TS-1 at a daily dose of 80 mg/body for 2 weeks. Surprisingly, the pathological examination revealed complete disappearance of cancer cells in the resected stomach and no cancer cells in the regional lymphnodes, judged grade 3 in pathological effectiveness. Case 2 of type 2 advanced gastric cancer was treated with TS-1 at a daily dose of 100 mg/body for 2 weeks and underwent surgery after a three-week interval due to the complication of pneumonia. The pathological effectiveness was judged grade 2 in the resected stomach, and no cancer cells were detected in the regional lymphnodes. In both cases, the postoperative course was uneventful, and no adverse effects were detected. In these cases, their high sensitivity to TS-1 was clearly confirmed, and now they have been treated with TS-1 for the postoperative adjuvant chemotherapy, and have undergone regular check-ups at our outpatient clinic in good condition. Recently, we performed the same protocol in 6 cases of advanced gastric cancer including these 2 cases and also in 4 cases of advanced colorectal cancer. This protocol was found useful for evaluating the pathological effect by TS-1. We consider the protocol quite useful and helpful in determining a suitable regimen for postoperative adjuvant chemotherapy.