Context: Increased radiation doses improve prostate cancer control but also increase toxicity to adjacent normal tissue. Proton radiation may attenuate adverse effects.
Objective: To determine long-term, patient-reported, dose-related toxicity.
Design, setting, and patients: We performed a post hoc cross-sectional survey of surviving participants in the Proton Radiation Oncology Group (PROG) 9509--a randomized trial comparing 70.2 Gy vs 79.2 Gy of combined photon and proton radiation for 393 men with clinically localized prostate cancer (stage T1b-T2b, prostate-specific antigen <15 ng/mL, and no radiographic evidence of metastasis). The estimated 10-year biochemical progression rate for patients receiving standard dose was 32% (95% confidence interval, 26%-39%) compared with 17% (95% confidence interval, 11%-23%) for patients receiving high dose (P < .001). We surveyed 280 of the surviving 337 patients (83%) from April 2007 to September 2008.
Main outcome measures: Prostate Cancer Symptom Indices, a validated measure of urinary incontinence, urinary obstruction and irritation, bowel problems, and sexual dysfunction, and related quality-of-life instruments.
Results: At a median of 9.4 years after treatment (range, 7.4-12.1 years), participants' demographic and clinical characteristics were similar. Patient-reported outcomes were reported as mean (SD) scale score for standard dose vs high dose: urinary obstruction/irritation (23.3 [13.7] vs 24.6 [14.0]; P = .36), urinary incontinence (10.6 [17.7] vs 9.7 [15.8]; P = .99), bowel problems (7.7 [7.8] vs 7.9 [9.1]; P = .70), sexual dysfunction (68.2 [34.6] vs 65.9 [34.7]; P = .65), and most other outcomes were also similar, although patients receiving standard dose whose cancers had more often progressed expressed less confidence that their cancers were under control (mean [SD] scale score for standard dose, 76.0 [25.4] vs high dose, 86.2 [17.9]; P < .001). Many patients characterized their urinary and bowel function as normal despite reporting symptoms that, for other prostate cancer patients before and early after cancer treatment, caused substantial distress.
Conclusion: Among men with clinically localized prostate cancer, treatment with higher-dose radiation compared with standard dose was not associated with an increase in patient-reported prostate cancer symptoms after a median of 9.4 years.