Hypofractionated passively scattered proton radiotherapy for low- and intermediate-risk prostate cancer is not associated with post-treatment testosterone suppression

Whoon Jong KilDepartment of Radiation Oncology, University of Florida, Gainesville, Florida, USA;University of Florida Proton Therapy Institute, Jacksonville, Florida, USA

Romaine C. Nichols JrDepartment of Radiation Oncology, University of Florida, Gainesville, Florida, USA;University of Florida Proton Therapy Institute, Jacksonville, Florida, USACorrespondence[email protected]

Bradford S. HoppeDepartment of Radiation Oncology, University of Florida, Gainesville, Florida, USA;University of Florida Proton Therapy Institute, Jacksonville, Florida, USA

Christopher G. MorrisDepartment of Radiation Oncology, University of Florida, Gainesville, Florida, USA;University of Florida Proton Therapy Institute, Jacksonville, Florida, USA

Robert B. Marcus JrDepartment of Radiation Oncology, University of Florida, Gainesville, Florida, USA;University of Florida Proton Therapy Institute, Jacksonville, Florida, USA

William MendenhallDepartment of Radiation Oncology, University of Florida, Gainesville, Florida, USA;University of Florida Proton Therapy Institute, Jacksonville, Florida, USA

Nancy P. MendenhallDepartment of Radiation Oncology, University of Florida, Gainesville, Florida, USA;University of Florida Proton Therapy Institute, Jacksonville, Florida, USA

Zuofeng LiDepartment of Radiation Oncology, University of Florida, Gainesville, Florida, USA;University of Florida Proton Therapy Institute, Jacksonville, Florida, USA

Joseph A. CostaDivision of Urology, University of Florida Shands Hospital, Jacksonville, Florida, USA

Christopher R. WilliamsDivision of Urology, University of Florida Shands Hospital, Jacksonville, Florida, USA

Randal H. HendersonDepartment of Radiation Oncology, University of Florida, Gainesville, Florida, USA;University of Florida Proton Therapy Institute, Jacksonville, Florida, USA

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Abstract

Background. To investigate post-treatment changes in serum testosterone in low- and intermediate-risk prostate cancer patients treated with hypofractionated passively scattered proton radiotherapy. Material and methods. Between April 2008 and October 2011, 228 patients with low- and intermediate-risk prostate cancer were enrolled into an institutional review board-approved prospective protocol. Patients received doses ranging from 70 Cobalt Gray Equivalent (CGE) to 72.5 CGE at 2.5 CGE per fraction using passively scattered protons. Three patients were excluded for receiving androgen deprivation therapy (n = 2) or testosterone supplementation (n = 1) before radiation. Of the remaining 226 patients, pretreatment serum testosterone levels were available for 217. Of these patients, post-treatment serum testosterone levels were available for 207 in the final week of treatment, 165 at the six-month follow-up, and 116 at the 12-month follow-up. The post-treatment testosterone levels were compared with the pretreatment levels using Wilcoxon's signed-rank test for matched pairs. Results. The median pretreatment serum testosterone level was 367.7 ng/dl (12.8 nmol/l). The median changes in post-treatment testosterone value were as follows: +3.0 ng/dl (+0.1 nmol/l) at treatment completion; +6.0 ng/dl (+0.2 nmol/l) at six months after treatment; and +5.0 ng/dl (0.2 nmol/l) at 12 months after treatment. None of these changes were statistically significant. Conclusion. Patients with low- and intermediate-risk prostate cancer treated with hypofractionated passively scattered proton radiotherapy do not experience testosterone suppression. Our findings are consistent with physical measurements demonstrating that proton radiotherapy is associated with less scatter radiation exposure to tissues beyond the beam paths compared with intensity-modulated photon radiotherapy.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Hypofractionated passively scattered proton radiotherapy for low- and intermediate-risk prostate cancer is not associated with post-treatment testosterone suppression

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Hypofractionated passively scattered proton radiotherapy for low- and intermediate-risk prostate cancer is not associated with post-treatment testosterone suppression

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