Abstract
OBJECTIVE: Microscopically positive resection margins (R1) in gastric cancer have been associated with poor outcomes, but evidence regarding its prognostic significance across different stages remains inconsistent. This study investigated the impact of R1 resection on survival outcomes and evaluated the prognostic significance of detailed pathological characteristics of margin involvement. METHODS: This retrospective study analyzed 10,165 patients who underwent curative-intent gastrectomy for gastric cancer between 2007 and 2021. Propensity score matching was performed at a 1:3 ratio between R1 (n=45) and R0 (n=130) cases. For R1 margins, detailed pathological assessment included involvement length, proportion, depth, and histological features. Survival outcomes were evaluated across all stages, and the impact of subsequent resection was analyzed. RESULTS: After propensity score matching, R1 resection showed significantly lower 5-year overall survival rates compared to R0 resection across all stages (stage I: 60.0% vs. 90.9%, P=0.008; stage II: 40.0% vs. 83.3%, P=0.001; stage III: 20.0% vs. 35.4%, P<0.001). In R1 cases, tumor involvement length ≤1 cm (P<0.001), proportion ≤10% (P=0.012), and mucosal-only involvement (P=0.004) were associated with better survival. Patients who underwent subsequent resection to achieve R0 status showed better survival than those with persistent R1 resection (53.8% vs. 26.7%, P<0.001) and comparable survival to matched R0 cases (53.8% vs. 46.9%, P=0.320). CONCLUSIONS: R1 resection significantly impairs survival across all stages of gastric cancer, with the extent and depth of microscopic involvement influencing prognosis. When R1 status is discovered postoperatively, subsequent resection should be considered to improve survival outcomes.