Trastuzumab With S-1 Plus Cisplatin in HER2-positive Advanced Gastric Cancer Without Measurable Lesions: OGSG 1202

BACKGROUND/AIM: Trastuzumab with S-1 plus cisplatin was proved to be effective for human epidermal growth factor receptor type 2 (HER2)-positive advanced gastric cancer with measurable lesions. However, the efficacy and safety of this regimen in the absence of measurable lesions are unknown. PATIENTS AND METHODS: Patients with HER2-positive gastric cancer without measurable lesions received cisplatin plus trastuzumab intravenously on day 1 and oral S-1 on days 1-14 of a 21-day cycle. The primary end-point was overall survival, and 40 patients were planned to be enrolled. RESULTS: Fifteen patients were enrolled. The median overall survival was 14.4 months. The 1- and 3-year overall survival rates were 66.7 % and 26.7 %, respectively. Major grade 3-4 adverse events included neutropenia (47%), anemia (40%), diarrhea (20%), nausea (20%), and anorexia (20%). CONCLUSION: Trastuzumab with S-1 plus cisplatin might be effective and tolerable for HER2-positive advanced gastric cancer without measurable lesions.