R1 Resection in Gastric Cancer: Marker of Tumor Biology Rather Than Surgical Failure

BACKGROUND Microscopically positive margins (R1) after gastrectomy are uncommon but are associated with poor outcomes. Whether R1 reflects inadequate surgery or aggressive tumor biology remains unclear. MATERIAL AND METHODS We retrospectively analyzed 28 patients who underwent R1 resection for gastric adenocarcinoma between 2010 and 2023. Clinicopathologic features, recurrence patterns, and overall survival (OS) were evaluated. Prognostic factors were identified using univariate and multivariate Cox regression. RESULTS After a median follow-up of 82 months, the 5-year OS was 21.4%. Recurrence occurred in 50% of patients, all of whom subsequently died. On univariate analysis, HER2 negativity (HR 0.60, 95% CI 0.41-0.87, P=0.007), high Ki-67 index (HR 1.03, 95% CI 1.01-1.05, P=0.004), poor differentiation (HR 2.40, 95% CI 1.26-4.55, P=0.008), advanced pathological stage (HR 15.87, 95% CI 3.79-66.40, P<0.001), high lymph node ratio (HR 245.63, 95% CI 20.60-2929.13, P<0.001), and signet ring histology (HR 5.29, 95% CI 1.94-14.43, P=0.001) were associated with inferior OS. Multivariate analysis confirmed signet ring histology (HR 6.00, 95% CI 1.32-27.22, P=0.020) and advanced pathological stage (HR 13.28, 95% CI 2.76-63.89, P=0.001) as independent adverse prognostic factors, whereas lymph node ratio demonstrated borderline significance (HR 35.77, 95% CI 0.98-1308.06, P=0.051). CONCLUSIONS Survival after R1 resection is determined mainly by tumor biology - particularly signet ring features and advanced stage - rather than surgical technique. These findings call for risk-adapted adjuvant strategies and refined prognostic models in this high-risk subgroup.