Risk factors of circumferential resection margin involvement in the patients with extraperitoneal rectal cancer

Purpose: Currently, circumferential resection margins (CRM) are used as a clinical endpoint in studies on the prognosis of rectal cancer. Although the concept of a circumferential resection margin in extraperitoneal rectal cancer differs from that in intraperitoneal rectal cancer due to differences in anatomical and biologic behaviors, previous reports have provided information on CRM involvement in all types of rectal cancer including intraperitoneal lesions. Therefore, the aim of this study was to analyze risk factors of CRM involvement in extraperitoneal rectal cancer. Methods: From January 2005 to December 2008, 306 patients with extraperitoneal rectal cancer were enrolled in a prospectively collected database. Multivariate logistic regression analysis was used to identify predictors of CRM involvement. Results: The overall rate of CRM involvement was found to be 16.0%. Multivariate analysis showed that male sex, larger tumor size (>= 4 cm), stage higher than T3, nodal metastasis, tumor perforation and non-sphincter preserving proctectomy (NSPP) were risk factors for CRM involvement. Conclusion: Male sex, larger tumor size (>= 4 cm), advanced T stage, nodal metastasis, tumor perforation, and NSPP are significant risk factors of CRM involvement in extraperitoneal rectal cancer. Given that postoperative chemoradiotherapy is recommended for patients with a positive CRM, further oncologic studies are warranted to ascertain which patients with these risk factors would require adjuvant therapy.