Phase II study of trastuzumab in combination with S-1 plus cisplatin in HER2-positive gastric cancer (HERBIS-1).

BACKGROUND: S-1, an oral fluoropyrimidine, plus cisplatin (SP) is a standard regimen for advanced gastric cancer (AGC) in East Asia. To date, no studies have evaluated the efficacy and safety of trastuzumab combined with SP in patients with human epidermal growth factor receptor type 2 (HER2)-positive AGC. METHODS: Patients with HER2-positive AGC received S-1 (80-120 mg per day) orally on days 1-14, cisplatin (60 mg m(-2)) intravenously on day 1, and trastuzumab (course 1, 8 mg kg(-1); course 2 onward, 6 mg kg(-1)) intravenously on day 1 of a 21-day cycle. The primary end point was response rate (RR); secondary end points included overall survival (OS), progression-free survival (PFS), time to treatment failure (TTF), and adverse events. RESULTS: A total of 56 patients were enrolled. In the full analysis set of 53 patients, the confirmed RR was 68% (95% confidence interval (CI)=54-80%), and the disease control rate was 94% (95% CI=84-99%). Median OS, PFS, and TTF were estimated as 16.0, 7.8, and 5.7 months, respectively. Major grade 3 or 4 adverse events included neutropaenia (36%), anorexia (23%), and anaemia (15%). CONCLUSIONS: Trastuzumab in combination with SP showed promising antitumour activity and manageable toxic effects in patients with HER2-positive AGC.