Distal margin requirements after preoperative chemoradiotherapy for distal rectal carcinomas: are < or = 1 cm distal margins sufficient?

BACKGROUND: Sphincter-sparing alternatives to abdominoperineal resection (APR) in the treatment of rectal cancer often are underused out of concern for inadequate distal margins and local failure. The present study addresses whether sphincter-sparing techniques with distal margins < or = 1 cm adversely influence oncological outcome in patients given preoperative chemoradiotherapy.
METHODS: Thirty-seven patients with rectal cancer < or = 8 cm from the anal verge were enrolled in the study. Preoperative external beam radiotherapy (5400 Gy) was administered together with continuous infusion of 5-fluorouracil (300 mg/m2/day). Surgical resection was performed in 36 patients with pathological assessment of tumor response and margins. Patients with sphincter-sparing resection and distal margins > 1 cm or < or = 1 cm and those who underwent APR were compared.
RESULTS: Thirty-six patients completed preoperative chemoradiotherapy, with successful sphincter-preservation in 28 patients. At a median follow-up of 33 months, there were 12 recurrences overall, which included 11 distant failures and four pelvic failures. Disease-free survival (DFS) was not different between those who had an APR compared with sphincter-sparing resection with distal margins < or = 1 cm. DFS was worse (P < .02) when radial margins were < or = 3 mm compared with > 3 mm.
CONCLUSIONS: Sphincter preservation is feasible in more than 75% of patients with tumors < or = 8 cm from the anal verge after preoperative chemoradiotherapy. Sphincter-sparing surgery with distal margins < or = 1 cm can be used without adversely influencing local recurrence or DFS. Limited radial margins (< or = 3 mm), however, are associated with increased disease recurrence.