Advances in Radiation Oncology (May 2020)

Gantry-Mounted Linear Accelerator–Based Stereotactic Body Radiation Therapy for Low- and Intermediate-Risk Prostate Cancer

  • Audrey T. Dang, MD,
  • Rebecca G. Levin-Epstein, MD,
  • David Shabsovich, BS,
  • Minsong Cao, PhD,
  • Christopher King, PhD, MD,
  • Fang-I. Chu, PhD,
  • Constantine A. Mantz, MD,
  • Kevin L. Stephans, MD,
  • Chandana A. Reddy, MS,
  • D. Andrew Loblaw, MD,
  • Patrick Cheung, MD,
  • Marta Scorsetti, MD,
  • Luca Cozzi, PhD,
  • Albert S. DeNittis, MD,
  • Yue Wang, MD,
  • Nicholas Zaorsky, MD,
  • Nicholas G. Nickols, MD, PhD,
  • Patrick A. Kupelian, MD,
  • Michael L. Steinberg, MD,
  • Amar U. Kishan, MD

Journal volume & issue
Vol. 5, no. 3
pp. 404 – 411

Abstract

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Purpose: To establish the safety and efficacy of gantry-mounted linear accelerator-based stereotactic body radiation therapy (SBRT) for low- and intermediate-risk prostate cancer. Methods: We pooled 921 patients enrolled on 7 single-institution prospective phase II trials of gantry-based SBRT from 2006 to 2017. The cumulative incidences of biochemical recurrence (defined by the Phoenix definition) and physician-scored genitourinary (GU) and gastrointestinal (GI) toxicities (defined per the original trials using Common Terminology Criteria for Adverse Events) were estimated using a competing risk framework. Multivariable logistic regression was used to evaluate the relationship between late toxicity and prespecified covariates: biologically effective dose, every other day versus weekly fractionation, intrafractional motion monitoring, and acute toxicity. Results: Median follow-up was 3.1 years (range, 0.5-10.8 years). In addition, 505 (54.8%) patients had low-risk disease, 236 (25.6%) had favorable intermediate-risk disease, and 180 (19.5%) had unfavorable intermediate-risk disease. Intrafractional motion monitoring was performed in 78.0% of patients. The 3-year cumulative incidence of biochemical recurrence was 0.8% (95% confidence interval [CI], 0-1.7%), 2.2% (95% CI, 0-4.3%), and 5.1% (95% CI, 1.0-9.2%) for low-, favorable intermediate-, and unfavorable intermediate-risk disease. Acute grade ≥2 GU and GI toxicity occurred in 14.5% and 4.6% of patients, respectively. Three-year cumulative incidence estimates of late grade 2 GU and GI toxicity were 4.1% (95% CI, 2.6-5.5%) and 1.3% (95% CI, 0.5-2.1%), respectively, with late grade ≥3 GU and GI toxicity estimates of 0.7% (95% CI, 0.1-1.3%) and 0.4% (95% CI, 0-0.8%), respectively. The only identified significant predictors of late grade ≥2 toxicity were acute grade ≥2 toxicity (P < .001) and weekly fractionation (P < .01), although only 12.4% of patients were treated weekly. Conclusions: Gantry-based SBRT for prostate cancer is associated with a favorable safety and efficacy profile, despite variable intrafractional motion management techniques. These findings suggest that multiple treatment platforms can be used to safely deliver prostate SBRT.