Systemic chemotherapy for gastric cancer with early recurrence after adjuvant S-1 monotherapy: a multicenter retrospective study.
S-1 monotherapy is one of the standard adjuvant treatments for patients with stage II and III gastric cancers. Early recurrence after S-1 adjuvant therapy has a poor prognosis. This study aimed to clarify the treatment outcomes of systemic chemotherapy and explore encouraging regimens. This was a multicenter retrospective study. Among gastric cancer patients who underwent curative gastrectomy followed by adjuvant S-1 monotherapy, patients who experienced a recurrence while receiving adjuvant therapy or within 6 months after completion and started systemic chemotherapy at four institutions between 2005 and 2015 were eligible. A total of 112 patients were included. The main treatment regimens were weekly paclitaxel (n = 38, 34%), irinotecan plus cisplatin (n = 31, 28%), capecitabine plus cisplatin (n = 7, 6%), and irinotecan monotherapy (n = 6, 5%). For all patients, median progression-free survival and overall survival were 3.7 and 11.4 months, respectively. Among 77 patients with measurable lesions, the overall response and disease control rates were 24.7% and 62.3%, respectively. Multivariate analyses for overall survival showed that Eastern Cooperative Oncology Group performance status 2 [hazard ratio (HR) 3.71; 95% confidence interval (CI) 1.78-7.73] and undifferentiated histological type (HR 2.04; 95% CI 1.35-3.44) were independent prognostic factors, and treatment regimens were not prognostic. Exploratory comparisons did not show statistically significant differences between treatment regimens. This study of the largest number of patients with early recurrence after S-1 adjuvant monotherapy demonstrated that the prognosis for patients treated by all regimens was similar and poor.