Continuous Effect of Radial Resection Margin on Recurrence and Survival in Rectal Cancer Patients Who Receive Preoperative Chemoradiation and Curative Surgery: A Multicenter Retrospective Analysis.

Purpose: To elucidate the proper length and prognostic value of resection margins in rectal cancer patients who received preoperative chemoradiotherapy (CRT) followed by curative total mesorectal excision (TME). Methods and materials: A total of 1476 rectal cancer patients staging cT3-4N0-2M0 were analyzed. All patients received radiation dose of 50.4 Gy in 28 fractions with concurrent 5-fluorouracil or capecitabine. Total mesorectal excision was performed 4 to 8 weeks after radiation therapy.

Results: The recurrence-free survival (RFS) at 5 years showed a significant difference between 3 groups: patients with circumferential resection margin (CRM) ≤1 mm, CRM 1.1 to 5 mm, and CRM >5 mm (46.2% vs 68.6% vs 77.5%, P<.001). Patients with CRM ≤1 mm showed a significantly higher cumulative incidence of locoregional recurrence (P<.001) and distant metastasis (P<.001) at 5 years compared with the other 2 groups. Patients with CRM 1.1 to 5 mm showed a significantly higher cumulative incidence of distant metastasis (P<.001), but not locoregional recurrence (P=.192), compared with those with CRM >5 mm. Distal resection margin (≤5 vs >5 mm) did not show any significant difference in cumulative incidence of locoregional recurrence (P=.310) and distant metastasis (P=.926).

Conclusion: Rectal cancer patients with CRM ≤1 mm are a high-risk group, with the lowest RFS. Patients with CRM 1.1 to 5 mm may be at intermediate risk, with moderately increased distant recurrence. Distal resection margin was not significantly associated with RFS in rectal cancer after neoadjuvant CRT and total mesorectal excision.