In a phase I/II trial reported in JAMA Oncology, Zilli et al found that single-fraction high-dose stereotactic body radiotherapy (SBRT) was associated with a high biochemical relapse–free survival rate in patients with localized prostate cancer.
Study Details
In the trial, 43 patients with localized prostate cancer at low or intermediate risk, with International Society of Urological Pathology grade group 1 or 2, and without significant tumor in the transitional zone were enrolled at five centers in the United States and Europe between 2017 and 2022. Patients received a 19-Gy single-fraction prostate SBRT course with urethra-sparing and intrafraction motion control. The primary outcome measure was biochemical relapse–free survival at 3 years, with an expected value of 96% included in the 95% confidence interval (CI).
Key Findings
Median follow-up was 55.3 months (interquartile range = 49.9–60.7 months).
Biochemical recurrence–free survival at 3 years was 92.9% (95% CI = 85.4%–100%), meeting the primary endpoint; biochemical recurrence–free survival at 5 years was 88.0%.
At 3 years, grade 2 genitourinary (GU) adverse events were observed in four patients (9.8%) and grade 2 gastrointestinal (GI) adverse events were observed in two patients (4.9%). One grade 3 adverse event—proctitis—was observed in one patient at 12 months; no grade 4 or higher adverse events were observed. Grade 2 or higher erectile dysfunction increased from 9 (21.4%) of 42 patients at baseline to 15 (38.4%) of 39 at 3 years. A significant minimally clinically important change in Expanded Prostate Cancer Index Composite scores was observed in 6 patients (14%) for GU scores and in 12 patients (28%) for sexual scores. Minimal effects on GI bother scores were observed.
The investigators concluded: “In this multicenter phase [I/II] trial, a single-fraction 19-Gy urethra-sparing SBRT met the primary endpoint, achieving a 3-year [biochemical recurrence–free survival] of 92.9%, with grade 2 GU and GI [adverse events] remaining below 10% and 5%, respectively, at 3 years. Longer follow-up is warranted to assess long-term disease control.”
Thomas Zilli, MD, of the Department of Radiation Oncology, Oncology Institute of Southern Switzerland, Bellinzona, Switzerland, is the corresponding author for the JAMA Oncology article.
DISCLOSURE: The study was funded by a grant from the Fondation pour les Recherches Médicales et Biologiques sur le Cancer and Varian Medical Systems. For full disclosures of the study authors, visit jamanetwork.com.
