Phase II Study of Chemoradiotherapy With S-1 and Low-Dose Cisplatin for Inoperable Advanced Gastric Cancer

Purpose: The results of a pilot study using S-1/low-dose cisplatin/radiotherapy led us to hypothesize that the initial chemoradiotherapy regimen would induce a 70% efficacy rate with a 10% pathologic complete response rate. Patients and Methods: Only patients with unresectable or incurable advanced gastric cancer were eligible. The patients received induction S-1 and cisplatin therapy with radiotherapy followed by chemotherapy alone. Results: Of the 30 patients recruited and assessed, 29 were eligible for clinical evaluation of measurable lesions. The response rate was 65.5%, with 19 with a partial response, 8 with no change, and 2 with progressive disease of 29 patients. Of the 30 patients recruited, 10 (33.3%) underwent stomach resection and D2 LN dissections. The pathologic complete response rate was 13.3% (4 patients), and the R0 resection rate was 100% (10 patients). The survival analysis showed a median survival time of 25 months. Grade 3 toxicity occurred in 66.7% for leukocytopenia, 33.3% for thrombocytopenia, 23.3% for nausea and appetite loss, and 6.7% for anemia, diarrhea, and renal dysfunction. Although all the patients had been hospitalized with a poor performance status with a giant tumor, 97% (29 of 30) could be discharged after the first cycle, resulting in an improvement in quality of life. Conclusion: Chemoradiotherapy could be a powerful regimen for controlling tumor progression in advanced gastric cancer, improving patients' quality of life with tolerable toxicity. A complete histologic response rate of >10% would be expected, even for large tumors with metastatic lesions.