Multicenter phase II study of triplet combination chemotherapy with paclitaxel, cisplatin, and S-1 for advanced gastric cancer (OGSG 0703).

124 Background: Docetaxel combined with cisplatin and 5-fluorouracil is active in advanced gastric cancer, but not generally accepted because of its substantial toxicities. We conducted a multicenter phase II study of triplet combination using paclitaxel, cisplatin and S-1 (PCS) as first-line treatment for advanced gastric cancer. Methods: Patients with previously untreated, locally advanced or metastatic measurable gastric cancer, a performance status < 2, age of 20-75 years, and adequate organ functions were given intravenous paclitaxel at 70 mg/m2 and cisplatin at 30 mg/m2 on days 1 and 15, plus oral S-1 at 40 mg/m2 b.i.d. on days 1 to 21, followed by 2-week rest, repeated every 5 weeks. Treatment was continued until disease progression or unacceptable toxicity occurred, or the patient refused the therapy. Study endpoints included overall response rate (ORR) as primary, progression free survival (PFS), overall survival (OS), and toxicity. Sample size of 40 patients was determined to reject the ORR of 55% under the expectation of 75% with a power of 80% and a one-sided α of 5%. Results: A total of 52 patients were enrolled in this study, among whom 49 were assessable for efficacy and 51 assessable for toxicity. ORR was 46.9% (95% CI: 32.5-61.7%). The median PFS and median OS were 5.4 months (95% CI: 4.1-7.0) and 11.5 months (95% CI: 7.3-16.1), respectively. Frequent grade 3/4 toxicities were neutropenia (51%), leucopenia (25%), anemia (20%), hyponatremia (16%), anorexia (14%), diarrhea (8%) and fatigue (8%). There was no treatment-related death. Conclusions: Triplet combination chemotherapy with PCS demonstrated superior feasibility with promising antitumor activity, though which did not meet the statistical hypothesis, for advanced gastric cancer.