Dose-volume histograms associated to long-term colorectal functions in patients receiving pelvic radiotherapy

Background and purpose: To correlate long-term colorectal dysfunctions following radical radiotherapy for bladder or prostate cancer with clinical parameters and dose-volume histogram parameters of the small intestine, rectum, and anal canal volume. Materials and methods: Seventy-one patients previously treated for bladder or prostate cancer were interviewed following CT-based radiotherapy of 60-70 Gy with questions concerning long-term colorectal dysfunctions. Median follow-up time was 30 months (range 12-109 months). Clinical parameters and parameters from the dose-volume histograms were correlated with colorectal dysfunctions (Spearman's test). Median and quartile values of all parameters were used as cut-off values for statistical analyses. A logistic regression model was used for analysis of urgency and incontinence in relation to median or maximum radiation dose to the anal canal volume. Results: Rectum length, volume and several dose-volume parameters from the anal canal volume and rectal volume were correlated with late organ dysfunctions. In a logistic model, fecal urgency and incontinence were dependent of dose-volume parameters from the anal canal volume. No relation between age or follow-up time and late effects were found. Dose-volume parameters of the small intestine were not related to any late dysfunctions. Conclusions: A relationship between several late anorectal dysfunctions and dose-volume parameters from the rectum and anal canal volume was demonstrated. It is recommended to exclude the anal canal volume from the high dose-volume and to apply rectal shielding whenever possible to prevent late anorectal dysfunctions