Systematic review and meta-analysis of studies of preoperative SBRT for early-stage luminal breast cancer

Preoperative stereotactic body radiotherapy (SBRT) has emerged as a precision locoregional strategy for early-stage luminal breast cancer. Systematic review and meta-analysis of prospective studies was carried out to estimate the pooled pathological complete response (pCR) rate and to identify its predictors and characterize safety and cosmetic outcomes with preoperative SBRT for early luminal breast cancer (clinical stage T1-2 N0-1 ER-positive HER2-negative). Eleven studies (428 patients) were included. Among 8 trials (n=277) reporting pCR data, a pooled pCR rate of 21.4% was found (95% CI 12.1-35.1; I² 77.0%). The irradiation-to-surgery interval was the only significant predictor of pCR (β= +0.045 per week; p <0.001; R² 98.9%), while absorbed dose, fractionation, and technique showed no independent association. Pooled late grade ≥ 3 toxicity was seen in 5.9% (95% CI 3.7-9.1) and excellent or good cosmesis was achieved in 88.3% (79.4-93.6) of patients. The authors conclude that preoperative SBRT achieves a clinically meaningul pCR rate in earley luminal breast cancer, with acceptable toxicity and preserved cosmesis. The irradiation-to-surgery interval is the dominant modifiable predictor of pathological response.