Treatment outcomes of patients with involved resection margin after rectal cancer surgery: A nationwide population‐based cohort study in South Korea

Background The involvement of resection margins after rectal cancer surgery by malignant tumors is a negative prognostic factor. Therefore, it is important to analyze treatment outcomes and establish adjuvant therapy. Methods The Health Insurance Review and Assessment Service collects data from medical institutions in South Korea. We reviewed the database of this prospectively collected cohort for patients who underwent curative resection for rectal cancer. Results Of the 5,620 patients, 113 (2.0%) were diagnosed with resection margin involvement after surgery. The resection margins of patients with mid‐rectal cancer, pathologic stage III, mucinous/signet ring cell carcinoma, and undergoing emergency surgery were more frequently involved. Neoadjuvant chemoradiotherapy was a significant preventive factor for resection margin involvement (odds ratio = 0.53; 95% confidence interval [CI], 0.32–0.87; p = 0.012). The OS of patients with adjuvant treatment was better than that of patients without adjuvant treatment (5‐year overall survival [OS]: 62.8% vs. 46.3%, p = 0.02). The administration of chemoradiotherapy was also significantly associated with better OS (hazard ratio = 0.36; 95% CI, 0.17–0.77; p = 0.009). Conclusion Efforts to acquire wider resection margins are necessary for patients with mid‐rectal cancer, pathologic stage III, mucinous/signet ring cell carcinoma, and emergency surgery. Neoadjuvant chemoradiotherapy was a significant preventive factor for involved resection margin. Patients with resection margin involvement showed better OS after adjuvant treatment than those without adjuvant treatment. The adjuvant chemoradiotherapy was helpful to prevent the worse prognosis of these patients. Efforts to acquire wider resection margins are necessary for patients with mid‐rectal cancer, pathologic stage III, mucinous/signet ring cell carcinoma, and emergency surgery. The adjuvant chemoradiotherapy was helpful to prevent the worse prognosis of these patients.