Evaluation of the safety and efficacy of stereotactic body radiotherapy for radio-recurrent prostate cancer: a systematic review and meta-analysis.

Background: Stereotactic body radiotherapy (SBRT) is pivotal in managing radio-recurrent prostate cancer (PCa). This study aims to comprehensively review its efficacy and associated severe toxicities.

Methods: A thorough review of PubMed and EMBASE databases up to July 2024 was conducted to assess recurrence-free survival (RFS) with salvage SBRT across various subgroups. Survival curves were reconstructed using WebPlotDigitizer and a newly developed shiny application.

Results: Thirty-six studies were analyzed, with 15 papers (682 patients) contributing to survival curve reconstruction. Median RFS was 36.2 months, with 2-, 3-, and 5-year rates of 64.8%, 50.7%, and 40.6%, respectively. Factors associated with improved RFS included whole-gland irradiation [focal vs. whole, hazard ratio (HR) 1.83 (95% CI: 1.16-2.87), p = 0.008], and higher biologically effective dose (BED) [120-138.1 Gy vs. 144-167.7 Gy, HR 1.40 (95% CI: 1.07-1.83), p = 0.015]. Severe (grade ≥ 3) acute and late genitourinary (GU) toxicities occurred in 1.4% (95% CI: 0.8-2.3) and 3.7% (95% CI: 2.6-4.9) of patients, respectively. Severe acute and late gastrointestinal (GI) toxicities were reported in 0.5% (95% CI: 0.2-1.1) and 0.4% (95% CI: 0.1-1.0) of patients, respectively. Combined severe GU and GI toxicities were observed in 5.8% (95% CI: 4.5-7.4) and 1.3% (95% CI: 0.7-2.2) of patients, respectively.

Conclusions: This study provides a comprehensive assessment of toxicities and conducts a pooled analysis of RFS for salvage SBRT in radio-recurrent PCa. Factors such as whole-gland irradiation, and higher BED show promise as prognostic indicators for RFS. However, confirmation through randomized controlled trials is essential due to the low levels of evidence and study heterogeneity.