Patient-level benefits of proton beam therapy (PBT) relative to photon therapy for prostate cancer (PC) continue to be the focus of debate. Although trials comparing the two modalities are underway, most are being conducted using "conventional" PBT (passive scattering/uniform scanning [PS/US]) rather than pencil beam scanning (PBS). The dosimetric benefits of PBS are well-known, but comparative data are limited. This analysis compares PBS toxicity rates with those of PS/US in a prospective multicenter registry.
We evaluated acute/late gastrointestinal (GI) and genitourinary (GU) toxicity rates for men with low-to-intermediate risk PC enrolled in PCG 001-09. Acute toxicities with the two techniques were compared using χ2 tests, and the cumulative incidence methods for late toxicity. Multivariable analyses (MVAs) for acute toxicity were performed using logistic regression, and cox proportional hazards models for late toxicity.
Patients were treated using PS/US (n = 1105) or PBS (n = 238). Acute grade ≥2 GI toxicity in PBS did not significantly differ from that with PS/US (2.9% and 2.1%, respectively; P = 0.47). Acute grade ≥2 GU toxicity was significantly higher with PBS (21.9% and 15.1%; P < 0.01). In MVA, PBS was significantly associated with increased acute grade ≥2 GU toxicity (RR = 1.57, p < 0.001). Late grade ≥2 GI and GU toxicities did not differ significantly between groups.
This is the first multi-institutional comparative effectiveness evaluation of PBT techniques in PC. Differences in acute GU toxicity warrant further evaluation, and highlight the urgent need for prospective data using PBT.
Clinical and translational radiation oncology. 2019 Aug 31*** epublish ***
Mark V Mishra, Rahul Khairnar, Søren M Bentzen, Gary Larson, Henry Tsai, Christopher Sinesi, Carlos Vargas, George Laramore, Carl Rossi, Lane Rosen, Mingyao Zhu, William Hartsell
Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States., Pharmaceutical Health Services Research, University of Maryland School of Pharmacy, Baltimore, MD, United States., Department of Epidemiology & Public Health, Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD, United States., ProCure Proton Therapy Center, Oklahoma City, OK, United States., ProCure Proton Therapy Center, Somerset, NJ, United States., Hampton University Proton Therapy Institute, Hampton, VA, United States., Department of Radiation Oncology, Mayo Clinic Arizona, Phoenix, AZ, United States., University of Washington, Department of Radiation Oncology, Seattle, WA, United States., California Protons Cancer Therapy Center, San Diego, CA, United States., Willis-Knighton Proton Therapy Center, Shreveport, LA, United States., Northwestern Medicine Chicago Proton Center, Warrenville, IL, United States.