Chronic effects of pelvic radiation therapy on anorectal function

PURPOSE: The long-term effect of 4,500 cGy of preoperative radiation on anorectal function has not been prospectively evaluated. METHODS: Anal manometry was performed on 20 patients with rectal carcinoma before and four weeks after receiving 4,500 cGy of external radiotherapy. Four patients underwent proctectomies, three died, and three refused follow-up. Ten patients were available for long-term follow-up and underwent anal manometry at 14 to 42 (average, 35.5) months after initial radiotherapy. RESULTS: No significant difference in mean maximum squeeze or resting pressures was found after radiation therapy. The sphincter profile and minimum sensory threshold were unchanged. The rectoanal inhibitory reflex was present in all patients. Nine patients reported normal anal function. One patient who was incontinent before treatment remained incontinent. CONCLUSION: Preoperative radiation therapy has a minimal chronic effect on anorectal function. Incontinence after sphincter-saving operations for rectal cancer should not be attributed to preoperative radiation therapy.