Long-term outcomes of patients with metastatic gastric cancer after initial S-1 monotherapy

Background S-1, an oral fluoropyrimidine, has been shown to have excellent activity against gastric cancer in two phase II studies and is widely used in Japan. However, the long-term outcomes of patients after S-1 monotherapy for metastatic gastric cancer are unclear. The aim of this study was to investigate the long-term outcomes in metastatic gastric cancer patients who had initially received S-1 monotherapy. Methods Ninety-two previously untreated patients with advanced gastric cancer received S-1 monotherapy as first-line chemotherapy at the National Cancer Center Hospital East, Kashiwa, Japan, and then the long-term outcomes and characteristics of long-term survivors were analyzed retrospectively. Multivariate analysis of prognostic factors was performed by the Cox proportional hazard method. Results With a median follow-up of 3.1 years, the median progression-free survival time was 4.6 months. The median survival time was 11.9 months, with 1-, 2- and 3-year survival rates of 49.1%, 22.8%, and 9.8%, respectively. Multivariate analysis showed that good performance status (P = 0.0004) and only one metastatic site (P = 0.0048) were significant independent prognostic factors. Among 48 patients with a single metastatic site, 22 with peritoneal metastasis had longer survival times (median survival, 24 months) than patients with metastasis at other sites. Among the nine 3-year survivors, six had peritoneal metastases alone. Conclusions The survival outcomes after S-1 monotherapy are promising, especially in patients with good performance status and a single metastatic site. Our findings suggest that, among patients with a single metastatic site, those with peritoneal metastases alone have a chance for long-term survival.