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.
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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.
Colaco RJ, Hoppe BS, Flampouri S, McKibben BT, Henderson RH, Bryant C, Nichols RC, Mendenhall WM, Li Z, Su Z, Morris CG, Mendenhall NP. Are you the author?
The University of Florida Proton Therapy Institute, Jacksonville, Florida; Baptist Health Medical Center, Department of Surgery, Jacksonville, Florida.
Reference: Int J Radiat Oncol Biol Phys. 2014 Nov 5. pii: S0360-3016(14)04060-7.