Proton therapy toxicity outcomes for localized prostate cancer: Long-term results at a comprehensive cancer center

Alan J Sosa; Michael K Rooney; Howard D Thames; Jeremiah W Sanders; David M Swanson; Seungtaek L Choi; Quynh-Nhu Nguyen; Henry Mok; Deborah A Kuban; X Ron Zhu; Shalin Shah; Lauren L Mayo; Karen E Hoffman; Chad Tang; Sean E McGuire; Narayan Sahoo; Xiaodong Zhang; Andrew K Lee; Thomas J Pugh; Usama Mahmood; John W Davis; Brian F Chapin; Paul Corn; Reena Kudchadker; Noveen Ausat; Steven J Frank

doi:10.1016/j.ctro.2024.100822

Proton therapy toxicity outcomes for localized prostate cancer: Long-term results at a comprehensive cancer center

Clin Transl Radiat Oncol. 2024 Jul 31:48:100822. doi: 10.1016/j.ctro.2024.100822. eCollection 2024 Sep.

Authors

Alan J Sosa¹, Michael K Rooney¹, Howard D Thames², Jeremiah W Sanders³, David M Swanson², Seungtaek L Choi¹, Quynh-Nhu Nguyen¹, Henry Mok¹, Deborah A Kuban¹, X Ron Zhu⁴, Shalin Shah¹, Lauren L Mayo¹, Karen E Hoffman¹, Chad Tang¹, Sean E McGuire¹, Narayan Sahoo⁴, Xiaodong Zhang⁴, Andrew K Lee⁵, Thomas J Pugh⁶, Usama Mahmood⁷, John W Davis⁸, Brian F Chapin⁸, Paul Corn⁹, Reena Kudchadker¹, Noveen Ausat¹, Steven J Frank¹

Affiliations

¹ Departments of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.
² Departments of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.
³ Departments of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.
⁴ Departments of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.
⁵ Texas Center for Proton Therapy, Irving TX, United States.
⁶ University of Colorado Denver, Aurora, CO, United States.
⁷ Torrance Memorial Hunt Cancer Institute, Torrance, CA, United States.
⁸ Departments of Urology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.
⁹ Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States.

Abstract

Background: Proton therapy (PT) has unique biologic properties with excellent clinical outcomes for the management of localized prostate cancer. Here, we aim to characterize the toxicity of PT for patients with localized prostate cancer and propose mitigation strategies using a large institutional database.

Methods: We reviewed medical records of 2772 patients with localized prostate cancer treated with definitive PT between May 2006 through January 2020. Disease risk was stratified according to National Comprehensive Cancer Network guidelines as low [LR, n = 640]; favorable-intermediate [F-IR, n = 849]; unfavorable-intermediate [U-IR, n = 851]; high [HR, n = 315]; or very high [VHR, n = 117]. Descriptive statistics and Kaplan-Meier estimates assessed toxicity and freedom from biochemical relapse (FFBR).

Results: Median follow-up was 7.0 years. The median dose was 78 Gy(RBE)(range: 72-79.2 Gy) in 2.0 Gy(RBE) fractions; 63 % of patients received 78 Gy(RBE) in 39 fractions, and 29 % received 76 Gy(RBE) in 38 fractions. Overall rates of late grade ≥3 GU and GI toxicity were 0.87 % and 1.01 %, respectively. Two patients developed grade 4 late GU toxicity and seven patients with grade 4 late GI toxicity. All patients experiencing severe late grade 4 toxicities were treated to 78 Gy(RBE) in 39 fractions with 80 Gy(RBE) dose to the anterior rectal wall and/or bladder neck. The 10-year FFBR rates for patients with LR to U-IR disease were compared between those treated with 76 and 78 Gy(RBE); the rates were 94.5 % (95 % confidence interval [CI] 92.4-96.0 %) and 93.2 % (95 % CI 91.3-95.7 %), respectively (log-rank p = 0.22).

Conclusions: Proton therapy is associated with low rates of late grade ≥3 GU and GI toxicity. While rare, late grade 4 toxicities occurred in nine (0.3 %) patients. De-escalation to a total dose of 76 Gy(RBE) yields excellent clinical outcomes for patients with LR to U-IR disease with the potential for significant reductions in grade ≥3 late toxicity.