Dose to the inferior rectum is strongly associated with patient reported bowel quality of life after radiation therapy for prostate cancer

Abstract

PurposeTo evaluate rectal dose and post-treatment patient-reported bowel quality of life (QOL) following radiation therapy for prostate cancer. MethodsPatient-reported QOL was measured at baseline and 2-years via the expanded prostate cancer index composite (EPIC) for 90 patients. Linear regression modeling was performed using the baseline score for the QUANTEC normal tissue complication probability model and dose volume histogram (DVH) parameters for the whole and segmented rectum (superior, middle, and inferior). ResultsAt 2-years the mean summary score declined from a baseline of 96.0–91.8. The median volume of rectum treated to ⩾70Gy (V70) was 11.7% for the whole rectum and 7.0%, 24.4%, and 1.3% for the inferior, middle, and superior rectum, respectively. Mean dose to the whole and inferior rectum correlated with declines in bowel QOL while dose to the mid and superior rectum did not. Low (V25–V40), intermediate (V50–V60) and high (V70–V80) doses to the inferior rectum influenced bleeding, incontinence, urgency, and overall bowel problems. Only the highest dose (V80) to the mid-rectum correlated with rectal bleeding and overall bowel problems. ConclusionsSegmental DVH analysis of the rectum reveals associations between bowel QOL and inferior rectal dose that could significantly influence radiation planning and prognostic models.