Prospective Safety and Patient-Reported Quality-of-Life Outcome for Prostate Cancer Treated with Image-Guided Compact Pencil-Beam Proton Unit

Abstract

To evaluate toxicity and patient-reported quality-of-life outcome for prostate cancer treated with a modern single-gantry pencil-beam scanning (PBS) proton unit. Men with localized prostate cancer treated consecutively at one institution with a single-gantry compact pencil-beam scanning (PBS) proton unit between 09/2014 – 07/2017 were identified from an institutional review board-approved registry protocol. Patients’ quality-of-life (QOL) questionnaires were prospectively collected at baseline and subsequent follow-ups. Patient characteristics and tumor histology were obtained by medical chart review. Patients without any follow-up or missing baseline assessment were excluded. Urinary symptoms and erectile dysfunction (ED) were assessed by the American Urological Association (AUA) Symptom Index and the Sexual Health Inventory For Men (SHIM) Score, respectively. Genitourinary (GU) and gastrointestinal (GI) toxicities were evaluated by physician according to Common Terminology Criteria for Adverse Events (CTCAE v.4.0) and collected at each follow up. Data was analyzed using two-tail Fisher’s exact test comparing each time point to their baseline. A total of 113 patients were prospectively enrolled. Median age was 68.4 (47.6-89.8). Median baseline PSA was 5.9 ng/mL. Median Gleason score was 7. NCCN Risk grouping for low-, intermediate-, and high-risk were 15.0%, 57.4%, and 32.7%, respectively. For those initially presenting with moderate-severe urinary symptoms (42.0%), more (45.8%-66.7%) reported mild urinary symptoms and most (87.5%-100%) had stable/improved AUA scores during the first year. The most common urinary complaints at baseline were increased frequency and urgency, and these symptoms improved after treatment at follow-up. Forty percent (40.3%) reported no/mild ED at baseline. This trended down slightly after treatment but remained stable at follow-ups (28%-32%). The percentage of men requiring ED medication was not different at follow-up (32.0%-43.2%) compared to baseline (43.4%). The rate of impotence refractory to medication at follow-up was low and similar to that at baseline (3%-6%). Acute grade 2 GU and GI toxicities were 6.6% and 0.8% at the end of treatment. There were one grade 3 urinary incontinence GU toxicity at 3 months and one grade 3 rectal bleeding GI toxicity at 1 year. Proton therapy with image-guidance using modern compact PBS for prostate cancer is safe. It may improve urinary symptoms with minimal impact on sexual QOL in patients with localized prostate cancer. Long-term follow up is needed to confirm these favorable results.