Anal sphincter dysfunction in patients treated with primary radiotherapy for anal cancer: a study with the functional lumen imaging probe

Background: Sphincter-sparing radiotherapy or chemoradiation are standard treatments for patients with anal cancer. The ultimate treatment goal is full recovery from anal cancer with preserved anorectal function. Unfortunately, long-term survivors often suffer from severe anorectal symptoms. The aim of the present study was to characterize changes in anorectal physiology after radiotherapy for anal cancer.Method: We included 13 patients (10 women, age 63.41.9) treated with radiotherapy or chemoradiation for anal cancer and 14 healthy volunteers (9 women, age 61.41.5). Symptoms were assessed with scores for fecal incontinence and low anterior resection syndrome. Anorectal physiology was examined with anorectal manometry and the Functional Lumen Imaging Probe.Results: Patients had a median Wexner fecal incontinence score of 5 (0-13) and a median LARS score of 29 (0-39). Compared to healthy volunteers, patients had lower mean (+/- SE) anal -resting (38 +/- 5 vs. 71 +/- 6, p<.001) and -squeeze pressures (76 +/- 11 vs. 165 +/- 15, p<.001). Patients also had lower anal yield pressure (15.5 +/- 1.3mmHg vs. 28.0 +/- 2.0mmHg, p<.001), higher distensibility, and lower resistance to flow (reduced resistance ratio of the anal canal during distension, q=5.09, p<.001). No differences were found in median (range) rectal volumes at first sensation (70.5 (15-131) vs. 57 (18-132) ml, p>.4), urge (103 (54-176) vs. 90 (32-212), p>.6) or maximum tolerable volume (173 (86-413) vs. 119.5 (54-269) ml, p>.10).Conclusion: Patients treated with radiotherapy or chemoradiation for anal cancer have low anal resting and squeeze pressures as well as reduced resistance to distension and flow.