Ultra-high single-dose radiation therapy (SDRT) for intermediate-risk prostate cancer is safe and associated with low toxicity, and it offers tumor control and quality-of-life outcomes comparable to those of curative hypofractionated stereotactic body radiotherapy (SBRT), according to a new study.
In the single-institution, phase 2 PROSINT proof-of-concept trial, investigators randomly assigned 30 men with organ-confined intermediate-risk prostate cancer to receive 24 Gy SDRT or extreme hypofractionated SBRT in 5 fractions of 9 Gy over 5 consecutive days. Each trial arm had 15 patients. The primary end point was toxic effects.
The median follow-up duration was 48 months. The time to appearance and duration of acute and late toxic effects did not differ between study arms, Carlo Greco, MD, of the Champalimaud Centre for the Unknown in Lisbon, Portugal, and colleagues reported in JAMA Oncology. Cumulative late actuarial urinary toxic effects did not differ for grade 1 and grade 2 or higher. Actuarial grade 1 late gastrointestinal (GI) toxic effects were comparable; no grade 2 or higher late GI toxic effects occurred.
In addition, both study arms experienced declines in PSA to less than 0.5 ng/mL by 3 months. PSA relapse occurred in 2 patients in the SBRT arm and 3 in the SDRT arm at a median of 26.6 and 27.3 months, respectively. The actuarial 4-year PSA relapse-free survival rates were 85.7% vs 77.1% for the SBRT and SDRT arms, respectively, according to the investigators.
The EPIC-26 (Expanded Prostate Cancer Index Composite-Short Form) median summary scores for the genitourinary and GI domains decreased transiently at 1 month and returned to pretreatment scores by 3 months in both arms, Dr Greco’s team reported.
“The study offers encouraging perspectives on the feasibility and safety of 24 Gy SDRT in organ-confined prostate cancer,” the authors concluded. “Despite the limitation of a small sample size, the SDRT PSA end points recapitulate the outcomes of curative extreme hypofractioned 5 × 9 Gy SBRT reported here and in the recent literature.”
Disclosure: Several study authors declared affiliations with the biotechnology industry. Please see the original reference for a full list of authors’ disclosures.
Greco C, Pares O, Pimentel N, et al. Safety and efficacy of virtual prostatectomy with single-dose radiotherapy in patients with intermediate-risk prostate cancer. Published online March 11, 2021. JAMA Oncol. doi:10.1001/jamaoncol.2021.0039