Dose-volume relationship of acute and late small bowel toxicity from radiation therapy for prostate cancer: a Veterans Affairs study

Abstract

The objective of this study was to characterize the dose-volume relationship of small bowel toxicity during prostate radiation therapy in a homogenous Veterans Affairs population using modern IMRT/VMAT radiation techniques. All records of patients receiving radiation therapy for prostate cancer at the Veterans Affairs Long Beach Hospital between 2009 and 2011 were analyzed (n = 73). Peritoneal space contents were contoured on each slice of the planning CT scan. A median dose of 75.6 Gy was delivered with either intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT). The small bowel constraint used was V45 < 200 cc. Median follow-up was 2.4 years. Toxicity was scored using CTCAE v4.0 to grade acute and late small bowel toxicity. Seventeen patients (23 %) experienced acute grade 1 small bowel toxicity. Twenty-seven patients (37 %) experienced acute grade 2 small bowel toxicity. There was 3 % grade 1 and 10 % grade 2 late small bowel toxicity. There was no grade 3 or higher acute or late bowel toxicity. The mean volume of a small bowel receiving a dose of 45 Gy was 58 cc, range (2–193 cc). Nineteen patients (26 %) received greater than 52 Gy, range (52–80 Gy) and had no late small bowel toxicity. Multivariate analysis showed that prior abdominal surgery predicted acute small bowel toxicity HR = 4.6 (95 % CI 1.24–20.5) p = 0.03. In this Veterans Affairs population of prostate cancer patients treated with radiation, V45 < 200 cc minimizes small bowel toxicity. However, we show this constraint can possibly be exceeded without significant short- and long-term complications. Further studies should explore maximum tolerated dose-volume relationship to maximize tumor control without increasing the small bowel toxicity profile.