Late radiotherapy-induced lower intestinal toxicity (RILIT) of intensity-modulated radiotherapy for prostate cancer: The need for adapting toxicity scales and the appearance of the sigmoid colon as co-responsible organ for lower intestinal toxicity

PurposeTo report on:1.Late radiotherapy-induced lower intestinal toxicity (RILIT) after intensity-modulated radiotherapy (IMRT) for prostate cancer.2.The correlation between late RILIT and volume parameters of the rectum, sigmoid colon and small bowel.Materials and methodsWe included 241 patients with a follow-up of ⩾18 months for this analysis. Late RILIT consisted of 8 different symptoms, comprising the 5 symptoms from the RTOG toxicity score supplemented with urgency, fecal incontinence and anal pain. Late RILIT and late RTOG toxicity were scored prospectively and correlated with:1.Different rectum, sigmoid colon and small bowel volume parameters.2.Patient-related morbidity.We calculated the median, quartile and percentiles for the different volume parameters and correlated them with grade 1–3 late RILIT.ResultsMedian follow-up was 42 months. Three patients developed grade 3 red blood loss. We registered grade 2 RILIT and RTOG toxicity in 13% and 10%, respectively, the most frequent grade 1 symptom being fecal urgency. The intermediate rectal volume parameters were significantly correlated with late RILIT. We were able to calculate cut-off dose–volume histograms (DVHs) that predict for grade 0–2 RILIT.ConclusionsAfter IMRT for prostate cancer, the overall incidence of grade ⩾2 RILIT is low. Cut-off DVHs can be used for patient counseling.