Prognostic factors in patients with pathological T3N0M0 gastric cancer: A multi-institutional, retrospective study (YCOG2202).

[AIM] Gastric cancer is one of the leading causes of cancer-related mortalities worldwide. According to the pathological TNM classification, T3N0M0, Stage IIA gastric cancer has been excluded from the S-1 adjuvant chemotherapy trials. Thus, the clinical impact of S-1 adjuvant chemotherapy in patients with pathological T3N0M0 cancer and the associated prognostic factors have not been elucidated. Consequently, we determined the prognostic factors in patients with pathological T3N0M0 gastric cancer and the efficacy of adjuvant chemotherapy.

[METHODS] From 2007 to 2018, 205 patients diagnosed with pathological T3N0M0 gastric cancer were enrolled at seven institutions. Recurrence-free and overall survival rates were evaluated. Univariate and multivariate survival analyses for recurrence-free and overall survival were performed, using the Cox proportional hazards model.

[RESULTS] The 5-year recurrence-free and overall survival rates were 84.7 % and 81.4 %, respectively. Although there was no difference in overall survival, multivariate analysis identified positive venous invasion as an independent risk factor for recurrence (p = 0.007, hazard ratio = 3.851). Adjuvant chemotherapy had no impact on both recurrence free and overall survival. However, the 5-year overall survival rates in the sub-cohort that completed adjuvant chemotherapy with S-1 were higher than those in the sub-cohort that did not complete the treatment (p = 0.019).

[CONCLUSION] The prognosis of patients with pathological T3N0M0 gastric cancer was relatively favorable. However, adjuvant chemotherapy was not identified as an independent risk factor and patients with venous invasion were at a high risk of recurrence. Therefore, a large-scale multi-institutional prospective study evaluating the efficacy of adjuvant chemotherapy for high risk pT3N0M0 is required.