Prognostic value of the proximal resection margin after curative distal gastrectomy for gastric cancer

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Background A negative resection margin is essential in gastric cancer surgery. However, the prognostic significance of proximal resection margin (PRM) length remains inconclusive. This study aimed to evaluate the association between PRM length and oncologic outcomes after curative distal gastrectomy. Methods This retrospective cohort study included 812 patients who underwent curative distal gastrectomy for gastric cancer between 2007 and 2020. Patients were stratified into three groups according to PRM length: <3 cm, 3–<5 cm, and ≥5 cm. Clinicopathologic characteristics and survival outcomes were compared across groups. Results Among the cohort, 172 patients (21.2%) had PRM <3 cm, 329 (40.5%) had PRM 3–<5 cm, and 311 (38.3%) had PRM ≥5 cm. Larger margins were associated with a higher proportion of lower-third tumors (24.4% vs. 38.0% vs. 72.0%, P < 0.001). No significant differences were observed among the three groups in 5-year overall survival (OS) (70.0% vs. 72.8% vs. 71.3%, P = 0.282) or 5-year disease-free survival (DFS) (66.4% vs. 68.5% vs. 68.7%, P = 0.322). Subgroup analyses showed no significant survival differences across T stage, gross appearance, tumor differentiation, or stage II–III disease. Although patients with stage I disease and shorter PRMs showed better OS (P = 0.029) and marginally better DFS (P = 0.050), PRM length was not independently associated with OS after multivariable adjustment. Conclusion Longer PRM length was not associated with improved oncologic outcomes once a negative margin was achieved.