Stereotactic body radiotherapy (SBRT) as a treatment for localized prostate cancer: a retrospective analysis

External beam radiotherapy (EBRT) is a standard treatment for localized prostate cancer, with recent advancements favoring a reduced number of treatment sessions. Stereotactic body radiotherapy (SBRT) is a form of radiotherapy that delivers higher doses per fraction, typically in five or fewer sessions. This retrospective study aims to evaluate the implementation of the PACE-SBRT protocol for localized prostate cancer at our center by assessing the incidence and severity of toxicity, as well as biochemical relapse-free survival.

We conducted a retrospective analysis of patients with localized prostate cancer treated with SBRT at the Iridium Network in Antwerp, Belgium, who were treated between January 1, 2020, and December 31, 2022. Data were extracted from electronic medical records and included descriptive information on patient outcomes. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.0. Acute toxicity was defined as events occurring within 90 days post-SBRT, whereas late toxicity was evaluated at 6 months, 1 year, 2 years, and 3 years post treatment. Biochemical recurrence was defined via the Phoenix criteria, as a rise in PSA levels of 2 ng/mL or more above the post treatment nadir.

A total of 267 patients met the eligibility criteria for this study. In total, 9% of patients were low risk, 51% were intermediate risk, and 40% were high risk. The cumulative incidence of Grade 2 or higher GU toxicity was 27%, and for GI toxicity, it was 2%. At 24 months, 11.5% (20/175) of patients experienced CTCAE grade 2 or higher GU toxicity, and 1.7% (3/175) experienced grade 2 or higher GI toxicity. Biochemical relapse occurred in 1.5% (4/267) of patients, leading to a 2-year biochemical relapse-free survival rate of 98.5%.

SBRT for localized prostate cancer has favorable oncological outcomes with a low incidence of Grade 2 or higher toxicity. The results of this study are consistent with findings from prospective trials, suggesting that SBRT is an effective treatment modality. Trial registration Retrospectively registered.