Phase 2 Study of Preoperative SABR for Early-Stage Breast Cancer: Introduction of a Novel Form of Accelerated Partial Breast Radiation Therapy.

We observed a 0% incidence of pCR with pre-operative SABR for early-stage BrCa as evaluated 6-8 weeks following treatment. Evolution of pCR may require longer than 6-8 weeks. Patients requiring post-operative whole breast radiotherapy after pre-operative SABR may be at increased risk for high-grade soft tissue toxicity. Further studies are needed to determine optimal patient selection, treatment methodology and timing of pathologic response evaluation.