Patients With Low Rectal Cancer Treated by Abdominoperineal Excision Have Worse Tumors and Higher Involved Margin Rates Compared With Patients Treated by Anterior Resection

PURPOSE: Patients with low rectal cancer have worse outcomes compared to those with upper rectal cancer. Reports suggest that low anterior resection may be oncologically superior to abdominoperineal excision, although no good evidence exists to support this. We looked at a recent series of patients with low rectal cancer to explore some of the issues. METHODS: We analyzed 153 patients from the MERCURY study with low rectal cancer (<= 6 cm from the anal verge). The median tumor height, percentage undergoing neoadjuvant therapy, involved margin rates, and degree of local invasion were compared for abdominoperineal excision vs low anterior resection. RESULTS: The mean tumor height from the anal verge was 2.9 cm for the patients with abdominoperineal excision vs 4.6 cm in the patients with low anterior resection. The involved margin rate was 20% overall, but was 31.9% for abdominoperineal excision vs 12% for low anterior resection. More patients who had abdominoperineal excision had neoadjuvant therapy (64% vs 41%) and a higher proportion had more locally advanced (T4) tumors. CONCLUSION: Patients undergoing abdominoperineal excision have higher involved margin rates; however, they had lower and more locally extensive tumors despite a greater proportion undergoing neoadjuvant therapy. Patients with low rectal cancer pose difficulties with regard to optimal management. Targeted strategies are needed to improve outcome in this complex and common cancer.