Rectal toxicity after proton therapy for prostate cancer: an analysis of outcomes of prospective studies conducted at the university of Florida Proton Therapy Institute

Int J Radiat Oncol Biol Phys. 2015 Jan 1;91(1):172-81. doi: 10.1016/j.ijrobp.2014.08.353. Epub 2014 Nov 5.

Abstract

Purpose: Study goals were to characterize gastrointestinal effects of proton therapy (PT) in a large cohort of patients treated for prostate cancer, identify factors associated with rectal bleeding (RB), and compare RB between patients receiving investigational protocols versus those in outcome-tracking protocols.

Methods and materials: A total of 1285 consecutive patients were treated with PT between August 2006 and May 2010. Potential pre-existing clinical and treatment-related risk factors for rectal toxicity were recorded. Common Terminology Criteria for Adverse Events version 3.0 was used to score toxicity.

Results: Transient RB was the predominant grade 2 or higher (GR2+) toxicity after PT, accounting for 95% of gastrointestinal events. GR1 RB occurred in 217 patients (16.9%), GR2 RB in 187 patients (14.5%), and GR3 in 11 (0.9%) patients. There were no GR4 or GR5 events. Univariate analyses showed correlations between GR2+ RB and anticoagulation therapy (P=.008) and rectal and rectal wall dose-volume histogram (DVH) parameters (P<.001). On multivariate analysis, anticoagulation therapy (P=.0034), relative volume of rectum receiving 75 Gy (V75; P=.0102), and relative rectal wall V75 (P=.0017) were significant predictors for G2+ RB. Patients treated with investigational protocols had toxicity rates similar to those receiving outcome-tracking protocols.

Conclusions: PT was associated with a low rate of GR2+ gastrointestinal toxicity, predominantly transient RB, which was highly correlated with anticoagulation and rectal DVH parameters. Techniques that limit rectal exposure should be used when possible.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Analysis of Variance
  • Anticoagulants / adverse effects
  • Fiducial Markers
  • Florida
  • Gastrointestinal Hemorrhage / etiology*
  • Gastrointestinal Tract / radiation effects
  • Humans
  • Male
  • Middle Aged
  • Prospective Studies
  • Prostatic Neoplasms / pathology
  • Prostatic Neoplasms / radiotherapy*
  • Proton Therapy / adverse effects*
  • Radiation Injuries / complications*
  • Radiation Injuries / pathology
  • Rectal Diseases / etiology*
  • Rectum / radiation effects*
  • Universities
  • Urinary Bladder

Substances

  • Anticoagulants