Single-center phase 1 trial of ablative preoperative single-fraction radiation dose escalation among patients with early-stage breast cancer

Single-fraction preoperative ablative stereotactic partial breast irradiation (sPBI) can be safely delivered in early-stage breast cancer with delayed time to surgery and high pathologic complete response rates. A phase 1 trial at UT Southwestern Medical Center (Dallas) examined the maximum tolerated dose (MTD) of sPBI and evaluated clinical outcomes among 44 patients with HR-positive, HER2-negative, cN0 invasive breast cancer not requiring chemotherapy. Patients received 30, 34, or 38 Gy using MR-LINAC. The maximum tolerated dose was not reached up to 38 Gy. High pathologic complete response rates combined with near complete response rates (up to 93.3%) were observed with prolonged time to surgery (>9 months).The authors conclude that these findings suggest that sPBI should be further investigated as a potential nonsurgical approach for selected early-stage HR-positive breast cancers.