Stereotactic Body Radiotherapy (SBRT) in Metachronous Oligometastatic Prostate Cancer: a Systematic Review and Meta-analysis on the Current Prospective Evidence

Objective: In contrast to traditional views of incurability, patients with oligometastatic disease present with an opportunity for disease eradication with aggressive treatment. There is mounting evidence in support of the role of stereotactic body radiotherapy (SBRT) in oligometastatic prostate cancer (OMPC).

Methods: MEDLINE and EMBASE were queried for prospective cohort studies reporting the outcomes of metachronous OMPC treated with SBRT. The primary outcome was overall local control. Secondary outcomes included androgen deprivation therapy-free survival (ADTFS), biochemical recurrence free survival (BCFS), and progression-free survival (PFS). When appropriate, these endpoints were combined in a meta-analysis.

Results: We screened 356 abstracts and identified 10 studies to include in our analysis, with a total of 653 patients and 1,111 lesions. The maximum number of lesions included in any single study ranged from 3 to 5. PET-CT staging occurred in 92.4% of all patients. SBRT dose varied, with BED ranging from 152 to 408. Only one Grade 3 bone toxicity was observed. Meta-analysis reported an overall local control rate of 97% (95% CI, 94-100). Median ADTFS was 24.7 months (95% CI, 20.1-29.2 months). Two-year BCFS, PFS, and ADTFS were 33% (95% CI, 11-55), 39% (95% CI, 24-54), and 52% (95%CI, 41-62), respectively. Patients treated with SBRT were half as likely to experience PSA progression than those on observation when looking at randomized control trial data alone.

Conclusion: SBRT appears to be effective in controlling overall disease burden in metachronous OMPC patients and is associated with minimal significant toxicity. The current prospective literature is scarce, and further prospective data are needed to guide treatment recommendations.

Advances In Knowledge: This study provides a comprehensive summary of the prospective evidence reporting the outcomes of SBRT in the management of OMPC patients. We quantify the rates of local control, biochemical-free recurrence, progression-free survival, and ADT-free survival through meta-analysis.