Systematic review and meta-analysis of stereotactic ablative radiotherapy for oligometastatic breast cancer

Stereotactic ablative radiotherapy (SABR) is increasingly used for oligometastatic breast cancer (OM; one to five metastases), but it is not clear in whom local ablation translates into systemic benefit. Systematic review and meta-analysis of studies published through March 2026 investigated outcomes with SABR for oligometastatic breast cancer. Twenty-five cohorts (1577 patients, 2211 lesions) were included. Pooled local control (LC) was 92.5% (95% CI 90.4-94.2) at one year and 84.6% (81.1-87.6) at two years, with no association with BED₁₀. At two years, progression-free survival (PFS) rate was 43.1% (34.4-52.5) and overall survival (OS) rate was 85.8% (76.0-92.0). Outcomes were consistenly superior in de novo OM compared with oligoprogressive (OP) disease: LC 95.7% versus 88.9% (p=0.001), PFS 50.9% versus 30.9% (p=0.003), OS 91.0% versus 65.8% (p=0.002), and time to next systemic therapy (TTNS) 18,5 versus 11.3 months. Within OP, lesion number was independently associated with TTNS (aHR 1.77 per lesion). Across four randomized trials, the pooled HR for PFS was 0.73; p=0.053). Grade ≥ 3 adverse events occurred in 21 of 1366 patients (1.50%). The authors conclude that SABR achieves durable LC with few treatment-related adverse events in all clinical contexts. Clinical context, rather than dose or metastatic site, determines whether this local effect translates into systemic benefit. Randomized evidence neither establishes nor excludes benefit.