Does postoperative chemotherapy improve overall survival of patients with ypT1-2N0 cancer?

BACKGROUND: Perioperative chemotherapy combined with curative gastrectomy has been increasingly represented the standard therapeutic strategy for resectable gastric cancer (GC). However, it is still unclear whether postoperative chemotherapy has a survival benefit for ypT1-2N0 gastric cancer patients who have undergone preoperative chemotherapy followed curative gastrectomy. METHODS: The data of patients who undergone neoadjuvant chemotherapy followed by gastrectomy and had pathological classification of ypT1-2N0 between March 2016 and December 2020 at Peking Union Medical College Hospital were retrospectively reviewed. Chi-square test was adopted to compare the difference between the patients with postoperative chemotherapy (pCHT) and without postoperative chemotherapy (no pCHT). Survival curves for overall survival (OS) were estimated using the Kaplan-Meier method, and the log-rank test was used to compare survival difference. Univariate and multivariate analyses for prognostic factors were based on the Cox regression. RESULTS: A total of 134 patients met the inclusion criteria and 56 (41.8%) of them have undergone postoperative chemotherapy. There were no statistically significant differences in demographic and clinicopathologic characteristics between pCHT group and no pCHT group (all p > 0.05). Postoperative chemotherapy was not associated with a significant improvement in overall survival (OS) (Hazard ratio [HR] 0.815, 95% confidence interval [CI] 0.403-1.650; p = 0.474). Subgroup analyses demonstrated survival was equivalent between pCHT and no CHT group in ypT1N0 patients (HR 0.832, CI 0.222-3.121; p = 0.786) and ypT2N0 patients (HR 1.284, CI 0.564-2.924; p = 0.551). Multivariable analysis identified that clinical T stage independently influenced prognosis (cT3 vs. cT2: HR 2.875, 95% CI 0.998-8.281, p = 0.050; cT4 vs. cT2: HR 7.382, 95% CI 2.569-21.211, p < 0.001). In clinical T3-4 patients, there was an overall survival benefit for postoperative chemotherapy (HR 0.270, 95% CI 0.114-0.634; p = 0.006). No survival benefit of postoperative chemotherapy was identified in clinical T2 patients (HR 0.689, 95% CI 0.200-2.372; p = 0.579). Furthermore, postoperative chemotherapy was proved to be an independently positive prognostic factor for clinical T3-4 patients (HR 0.132, 95% CI 0.051-0.345; p < 0.001). CONCLUSION: Postoperative chemotherapy might offer survival benefit to patients with ypT1-2N0 gastric cancer whose clinical T stage was T3-4 before preoperative chemotherapy.