22 Background: Limited data exist comparing contemporary technologies in the treatment of prostate cancer. Proton beam therapy (PBT) and intensity-modulated radiation therapy (IMRT) are both accepted ways of delivering high-dose radiation. We evaluated patient-reported quality of life (QOL) outcomes from two modern prospective cohorts treated with either PBT or IMRT. Methods: QOL data for 153 patients treated with IMRT and collected by the PROST-QA consortium using the Expanded Prostate Cancer Index Composite instrument were compared to data for 95 patients treated on protocol between 2004 and 2008 at the Massachusetts General Hospital with PBT using the Prostate Cancer Symptoms Index instrument. Mean score changes from baseline were compared using the Satterthwaite t-test. Clinically meaningful decline was defined as a score drop exceeding half the standard deviation of the baseline value. Results: Both cohorts had a similar distribution of Gleason score and baseline PSA though the IMRT cohort was older (median age 69 vs. 64, p<.0001). Treatment dose range was 75.6-79.2 Gy for IMRT and 74-82 CGE for PBT. Neither group received hormonal therapy. By 3 months after treatment there was a significant worsening in the bowel domain for the IMRT but not PBT cohort (15.9 point reduction vs. 1.5, p<.0001) which normalized by 12 months. Post-treatment scores were also lower in the urinary irritation domain (13.8 point reduction vs. 5.5, p<.0001) and in the urinary incontinence domain (7.3 point reduction vs. 1.5, p=.002) for IMRT but were similar by 24 months. All immediate post-treatment score changes in the IMRT but not PBT cohort were clinically meaningful. A steady decline in the sexual function domain was seen in both groups but the difference was not significant. Conclusions: In this non-randomized comparison using two validated QOL instruments measuring similar domains, PBT appears to be associated with lower gastrointestinal and urinary toxicity early after treatment with similar late outcomes. While subject to selection bias, these preliminary data suggest transient differences in toxicity patterns underscoring the rationale for a randomized controlled trial.
Comparative Analysis of 5-Year Clinical Outcomes and Patterns of Failure of Proton Beam Therapy Versus Intensity Modulated Radiation therapy for Prostate Cancer in the Postoperative Setting