PURPOSE:Preoperative radiotherapy improves local control in rectal cancer treatment,but there are fewreports on the influence of radiotherapy on anorectal function.The aim of the present study was to assess late effects of short-course,high-dose radiotherapy on anorectal function after low anterior resection for rectal cancer.METHODS:Sixty-four patients,randomized within the Stockholm Radiotherapy Trials and operated on with lowanterior resectionwith or without preoperative radiotherapy(mean,14 years),previously were followed up with quality-of life questionnaires,clinical examination,anorectal manometry,and endoanal ultrasound.Twenty-one patients had received preoperative radiotherapy of the rectum and 43 patients had been treated with surgery alone.RESULTS:Impaired anorectal function was common after low anterior resection for rectal cancer and the risk was increased after radiotherapy.Irradiated patients had significantly more symptoms of fecal incontinence(57 vs.26 percent,P = 0.01),soiling(38 vs.16 percent,P = 0.04),and significantly more bowel movements per week(20 vs.10,P = 0.02).At anorectal manometry,irradiated patients had significantly lower resting(35 mmHg vs.62 mmHg,P < 0.001)and squeeze pressures(104 mmHg vs.143 mmHg,P = 0.05).At endoanal ultrasound,irradiated patients had significantly more scarring of the anal sphincters(33 vs.13 percent,P = 0.03).There were no significant differences in quality-of-life scores between irradiated and nonirradiated patients;however,patients with anal incontinence had significantly lower quality-of-life scores compared to continent patients.CONCLUSIONS:Short-course radiotherapy,including the anal sphincters,impairs anorectal function and increases gastrointestinal symptoms permanently when the anal sphincters are irradiated. PURPOSE: Preoperative radiotherapy improves local control in rectal cancer treatment, but there are fewreports on the influence of radiotherapy on anorectal function. The aim of the present study was to assess late effects of short-course, high-dose radiotherapy on anorectal function after low anterior resection for rectal cancer. METHODS: Sixty-four patients, randomized within the Stockholm Radiotherapy Trials and operated on with lowanterior resectionwith or without preoperative radiotherapy (mean, 14 years), previously were followed up with quality-of-life questionnaires, clinical examination, anorectal manometry, and endoanal ultrasound.Twenty-one patients had had received radiotherapy of the rectum and 43 patients had been treated with surgery alone .RESULTS: Impaired anorectal function was common after low anterior resection for rectal cancer and the risk was increased after radiotherapy. Irradiated patients had significantly more symptoms of fecal incontinence (57 vs. 26 percent, P = 0.01 ), soiling (38 vs.16 percent, P = 0.04), and significantly more bowel movements per week (20 vs. 10, P = 0.02) .At anorectal manometry, irradiated patients had significantly lower resting (35 mmHg vs.62 mmHg , P <0.001) and squeeze pressures (104 mmHg vs.143 mmHg, P = 0.05) .At endoanal ultrasound, irradiated patients had significantly more scarring of the anal sphincters (33 vs.13 percent, P = 0.03) significant differences in quality-of-life scores between irradiated and nonirradiated patients; however, patients with anal incontinence had significantly lower quality-of-life scores compared to continent patients. CONCLUSIONS: Short-course radiotherapy, including the anal sphincters, impairs anorectal function and increases gastrointestinal symptoms permanently when the anal sphincters are irradiated.