Oligorecurrent Prostate Cancer and Stereotactic Body Radiotherapy: Where Are We Now? A Systematic Review and Meta-analysis of Prospective Studies

Context: The optimal management of oligometastatic prostate cancer (PCa) is still debated. Objective: The purpose of the present systematic review and meta-analysis is to collect the available evidence to date to better define the role of stereotactic body radiotherapy (SBRT) in selected patients with oligorecurrent PCa. Evidence acquisition: Study methodology complied with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). All prospective studies including PCa patients with nodal and/or bone oligometastases (one to five lesions) were considered eligible. Heterogeneity between study-specific estimates was tested using chi-square statistics and measured with the I2 index. A pooled estimate was obtained by fitting both fixed-effect and DerSimonian and Laird random-effect model. Evidence synthesis: Overall, six works (two randomized and the remainder observational) published between 2013 and 2020 were considered eligible. Globally, data from 445 patients were incorporated, of whom 396 were treated with SBRT (329 in observational studies and the remaining 67 in randomized ones). Regarding local progression-free survival (PFS), five studies reported values close to 100%, while one reported a value of 80% in the observation arm. The benefit in terms of biochemical PFS brought by SBRT was evident in all considered studies. Such a difference in cumulative probabilities between the intervention arm and the comparator arm is maintained even 24 mo after the baseline. All studies but one considered toxicity among the endpoints of interest. Most events were classified as either G1 or G2, and the only G ≥ 3 adverse event was reported in one trial. Conclusions: SBRT is highly cost effective, safe, and with an almost inexistent toxicity risk that makes it the perfect candidate for the optimal management of PCa oligometastatic patients. However, more solid data and a higher level of evidence are needed to affirm its role in the management of these patients. Patient summary: In this work, we reviewed available evidence on the use of stereotactic body radiotherapy in treating oligometastatic prostate cancer patients. We found good evidence that radiotherapy brings important benefits in overall treatment efficacy without major side effects.