Timing and site-specific trends of recurrence in patients with pathological stage II or III gastric cancer after curative gastrectomy followed by adjuvant S-1 monotherapy

Background Adjuvant S-1 monotherapy prolongs the survival of patients with pathological stage II or III gastric cancer undergoing D2 gastrectomy. This therapeutic regimen is standard in Japan. Unfortunately, some patients who undergo this treatment suffer from recurrent disease. However, information regarding the timing and site-specific trends of recurrence is insufficient. Methods Among 396 patients who underwent D2 gastrectomy followed by adjuvant S-1 monotherapy between 2008 and 2012, 122 experienced a recurrence. We retrospectively determined the timing and sites of recurrence. Results The median RFS of the 122 patients was 19.5 months, and their 1-, 3- and 5-year RFS rates were 67.2%, 23.0% and 5.7%, respectively. There were no significant differences in RFS among disease substages. Local recurrence, lymph node involvement and peritoneal and hematogenous metastases were found in 6, 25, 63 and 42 patients, respectively. Approximately 10% of patients presented with contemporaneous sites of recurrence. Local recurrence and lymph node metastasis plateaued 3 years after gastrectomy. Peritoneal and hematogenous metastasis increased within 5 years after surgery. In patients with hematogenous metastasis, the number of liver metastases plateaued but increased in others. Conclusions In patients with recurrent disease who underwent D2 gastrectomy followed by adjuvant S-1 monotherapy, 80% of recurrences occur within 3 years after gastrectomy. The timing of recurrence is not significantly different among substages. Although the rates of local recurrence and lymph node and liver metastasis plateau after 3 years, peritoneal and the other hematogenous metastases increase within 5 years.