3226 - Long-Term Outcomes Following Proton Therapy for Prostate Cancer in Men Ages 50 and Younger
Presenter(s)
M. Fortna, N. P. Mendenhall, D. A. Lichlyter, S. Jean-Baptiste, W. M. Mendenhall, R. C. Nichols Jr, and C. M. Bryant; Department of Radiation Oncology, University of Florida College of Medicine, Jacksonville, FL
Purpose/Objective(s): To report the long-term outcomes of men ages 50 and younger treated for localized prostatic adenocarcinoma with image guided proton therapy (PT).
Materials/Methods: We report 5- and 10-year outcomes from a cohort of men (n=85) with localized prostate cancer treated with PT between 2006 and 2017 at our institution. Forty-eight percent of men had low-, 46% had intermediate-, and 6% had high-risk prostate cancer respectively. Median PT dose was 78 CGE (range, 74 – 82) delivered at 2 CGE per fraction. Androgen deprivation therapy was received by nine (11%) men for a median six months. Biochemical control was defined using the Phoenix Definition. Physician-reported toxicity scoring was based on Common Terminology Criteria for Adverse Events Version 5.0. Patient-reported outcomes were assessed with the International Prostate Symptom Score and Expanded Prostate Index Composite (EPIC). Freedom from Biochemical Failure was tabulated using the Kaplan-Meier Method.
Results: Median follow-up was 12.3 years (range, 1.58 - 17.4). The 5- and 10-year FFBF rates for patients were 98.8% and 95.4% respectively. Three of the 85 patients developed disease progression at 10 years. All three had biochemical progression, one with concurrent regional/nodal metastases. Grade 2+ gastrointestinal toxicity occurred in 2 (2.35%) patients and grade 3+ urologic toxicity occurred in 2 patients (2.35%). The median EPIC summary scores for urinary and bowel outcomes were 97.1 and 98.1 at baseline, and 95.8 and 96.4 at 10 years respectively. The median EPIC sexual summary score was 82.7 at baseline and 69.2 at 10 years respectively. Two patients developed second cancers and both were out of field. One occurred in the submandibular gland 7 years after treatment and the other in the pancreas 10 years after treatment.
Conclusion: PT provides excellent tumor control for patients younger than 50 years old with localized prostate cancer with a low risk for high grade toxicities. No in-field secondary cancers were observed. Findings in this relatively small population should be confirmed within larger study populations.