Image-guided hypofractionated proton beam therapy for low-risk prostate cancer: Analysis of quality of life and toxicity, PCG GU 002.

Aim: This interim analysis evaluated changes in quality of life (QOL), American Urological Association Symptom Index (AUA), or adverse events (AEs) among prostate cancer patients treated with hypofractionation.

Background: Results for hypofractionated prostate cancer with photon therapy are encouraging. No prior trial addresses the role of proton therapy in this clinical setting.

Materials And Methods: Forty-nine patients with low-risk prostate cancer received 38-Gy relative biologic effectiveness in 5 treatments. They received proton therapy at 2 fields a day, magnetic resonance imaging registration, rectal balloon, and fiducial markers for guidance pre-beam. We evaluated AEs, Expanded Prostate Index Composite (EPIC) domains, and AUA at pretreatment and at 3, 6, 12, 18, and 24 months. An AUA change >5 points and QOL change of half a standard deviation (SD) defined clinical significance.

Results: Median follow-up was 18 months; 17 patients reached follow-up of ≥24 months. For urinary function, statistically and clinically significant change was not seen (maximum change, 3). EPIC urinary QOL scores did not show statistically and clinically significant change at any end point (maximum, 0.45 SD). EPIC bowel QOL scores showed small but statistically and clinically significant change at 6, 12, 18, and 24 months (SD range, 0.52-0.62). EPIC sexual scores showed small but statistically and clinically significant change at 24 months (SD, 0.52). No AE grade ≥3 was seen.

Conclusions: Patients treated with hypofractionated proton therapy tolerated treatment well, with excellent QOL scores, persistently low AUA, and no AE grade ≥3.