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

Abstract

Background and purposeTo 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 methodsSeventy-one patients previously treated for bladder or prostate cancer were interviewed following CT-based radiotherapy of 60–70Gy 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. ResultsRectum 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. ConclusionsA 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.