Purpose: The purpose of this study is to investigate the influence of radiotherapy (RT) on anorectal function and radiation-induced toxicity in patients with prostate cancer.
Materials and methods: Fifty-four patients who were treated with RT for prostate cancer (T1c-4N0-1M0) were evaluated. To assess the changes in anorectal function, two consecutive anorectal manometry readings were performed in patients, before and after 4-6 months of RT. Late gastrointestinal (GI) toxicity was defined as symptoms occurring more than 6 months after RT. The median radiation dose was 70.0 Gy (range, 66.0 to 74.0 Gy). Whole pelvis field RT was performed in 16 patients (29.6%). Grade of late radiation toxicity was defined in accordance to the severity of symptoms (Gulliford's scoring system).
Results: The median follow-up period was 60 months. Resting anal pressure (p=0.001), squeeze pressure (p < 0.001), and urge to defecate volume (p=0.025) were significantly reduced after RT. Fourteen patients (25.9%) experienced late GI toxicities. Among them, nine (16.7%) showed severe (grade ≥ 2) late toxicities. Elevated resting and squeeze external anal sphincter pressure prior to RT and large urge to defecate volumes after RT were associated with the occurrence of late GI toxicities.
Conclusion: RT caused symptomatic anorectal dysfunction and resulted in a weakened anal sphincter. Increased urge to defecate volumes after RT were related to late GI toxicities. Elevated resting and squeeze anal sphincter pressure prior to RT rodcan be used to identify patients with an increased risk of late GI toxicities.
Keywords: Anorectal manometry; Prostatic neoplasms; Radiation toxicity.