KEY POINTS
- SABRINA included 25 cohorts comprising 1,577 patients and 2,211 irradiated lesions. Thirteen cohorts represented de novo oligometastatic disease, four oligoprogression and eight mixed populations.
- Local ablation was consistently effective: pooled local control was 92.5% at one year (95% CI 90.4–94.2) and 84.6% at two years (81.1–87.6).
- Systemic disease control was substantially less durable. Across eligible cohorts, pooled 2-year PFS was 43.1% and 2-year OS 85.8%, illustrating the distinction between controlling the irradiated lesion and altering the metastatic disease course.
- Clinical setting strongly separated outcomes. De novo oligometastatic versus oligoprogressive disease produced 95.7% vs 88.9% one-year LC, 50.9% vs 30.9% two-year PFS, and 91.0% vs 65.8% two-year OS.
- Time to next systemic therapy followed the same pattern: weighted mean duration was 18.5 months in de novo oligometastatic versus 11.3 months in oligoprogressive disease. In one adjusted oligoprogression cohort, each additional treated lesion was associated with earlier systemic-therapy change (HR 1.77 per lesion).
- Across four randomized trials, adding SABR produced a pooled PFS HR of 0.73 (95% CI 0.53–1.00; p=0.053). Three trials were individually negative; OLIGOMA was positive but closed early after enrolling 87 patients. The pooled evidence therefore neither establishes nor excludes a clinically meaningful systemic benefit.
- Treatment was generally safe: grade ≥3 treatment-related toxicity occurred in only 21/1,366 patients, pooled 1.50%, with no treatment-related deaths. No convincing relationship between cohort-level BED10 and local control was identified.
CLINICAL TAKEAWAY
For oligometastatic breast cancer, SABR is very good at what it physically targets. The unresolved question is whether that excellent local control changes the course of systemic disease—and current randomized evidence is still insufficient, particularly when de novo oligometastatic and oligoprogressive disease are mixed together.