Circumferential Resection Margin Status as a Predictive Factor for Recurrence in Preoperative MRI for Advanced Lower Rectal Cancer Without Preoperative Therapy

BACKGROUND: In Japan, total mesorectal excision plus lateral lymph node dissection without preoperative therapy is the standard treatment for advanced lower rectal cancer. Although long-term oncologic outcomes with preoperative therapy based on circumferential resection margin status in preoperative MRI has been reported, outcomes without preoperative therapy are unknown. OBJECTIVE: This study evaluated long-term oncologic outcomes of radical surgery without preoperative therapy in advanced lower rectal cancer based on circumferential resection margin status in preoperative MRI, with the aim of defining appropriate patient populations for preoperative therapy. DESIGN: This retrospective analysis compared long-term oncologic outcomes with preoperative MRI in patients with lower rectal cancer. SETTINGS: Patients were identified through a database managed by our institute. PATIENTS: In total, 338 patients with lower rectal cancer who underwent radical surgery between 2000 and 2014 at the National Cancer Center Hospital without preoperative therapy were included. MAIN OUTCOME MEASURES: The main outcome was relapse-free survival. RESULTS: The median follow-up period was 61.7 months (range, 3-153 months). Five-year relapse-free survival rates in MRI-predicted circumferential resection margin negative patients and positive patients were 76.0% and 55.6% (p < 0.001). Univariate and multivariate analyses revealed pN stage (HR, 2.35; 95% CI, 1.470-3.770; p < 0.001), lymphatic invasion (HR, 2.03; 95% CI, 1.302-3.176; p = 0.002), venous invasion (HR, 2.15; 95% CI, 1.184-3.9; p = 0.01), surgical procedure (HR, 1.72; 95% CI, 1.115-2.665; p = 0.01), and MRI-predicted circumferential resection margin (HR, 1.850; 95% CI, 1.206-2.838; p = 0.0051) to be independent risk factors for postoperative recurrence. LIMITATIONS: This study was retrospective in design. CONCLUSIONS: Magnetic resonance imaging-predicted circumferential resection margin was associated with relapse-free survival without preoperative therapy, indicating its potential for use in selecting optimal preoperative therapy.

Automated summary

This study evaluated the long-term oncologic outcomes of radical surgery without preoperative therapy in advanced lower rectal cancer based on circumferential resection margin status in preoperative MRI. The study found that preoperative MRI-predicted circumferential resection margin was associated with relapse-free survival without preoperative therapy, indicating its potential for use in selecting optimal preoperative therapy.