Phase II trial of capecitabine plus modified cisplatin (mXP) as first-line therapy in Japanese patients with metastatic gastric cancer (KSCC1104)

Capecitabine plus cisplatin (XP) is a standard therapy for metastatic gastric cancer (mGC). However, while results from previous phase III trials suggested that the cisplatin dosage should be reduced in Japanese patients, no clinical data exist to support this. Here, we conducted a multicenter study to evaluate the efficacy and safety of modified XP (mXP) in Japanese patients with mGC. Patients with previously untreated mGC received mXP (cisplatin 60 mg/m(2) on day 1 plus capecitabine 1000 mg/m(2) twice daily on days 1-14) every 3 weeks. The primary endpoint was the Response Evaluation Criteria in Solid Tumors-confirmed overall response rate (ORR). A sample size of 40 was planned for a threshold ORR of 30% and an expected value of 50%, with a one-sided alpha of 0.05 and a beta of approximately 0.2. Forty-two patients were enrolled. One patient did not fulfill the eligibility criteria; therefore, a total of 41 patients were assessed. The results were as follows: complete response in 2 patients, partial response in 16, stable disease in 14, progressive disease in 8, and no evaluation in 1. The confirmed ORR was 43.9% (95% confidence interval 28.7-59.1%). The median progression-free survival and median overall survival were 4.6 and 11.3 months, respectively. The most common grade 3 or 4 adverse events were neutropenia (37.5%), anemia (24.4%), anorexia (24.4%), and nausea (12.2%). First-line chemotherapy with mXP in Japanese patients with mGC did not reach its primary objective. However, it did show a promising response rate and an acceptable tolerability profile.