Tumour response 3 months after neoadjuvant single-fraction radiotherapy for low-risk breast cancer.

Introduction Standard treatment for early-stage invasive breast cancer (BCa) consists of breast-conserving surgery and several weeks of adjuvant radiotherapy (RT). Neoadjuvant single-fraction RT is a novel approach for early-stage BCa. We sought to investigate the effect of delaying surgery after neoadjuvant RT with respect to the rate of pathologic response (pR). Methods Women 65 years of age or older with a new diagnosis of stage I luminal A BCa were eligible for inclusion. A single 20 Gy dose to the primary breast tumour was given, followed by breast-conserving surgery 3 months later. The primary endpoint was the pR rate assessed by microscopic evaluation using the Miller-Payne system. Results To date, 10 patients have been successfully treated. Median age of the patients was 72 years (range: 65-84 years). In 8 patients, neoadjuvant RT resulted in a tumour pa with median residual cellularity of 3%. No immediate RT complications other than mild dermatitis were noted. Conclusions This study demonstrates a method for delivering single-fraction RT that can lead to a high level of pR in most patients. Continued accrual to this study and subsequent trials are needed to determine the feasibility, safety, and role of this novel technique in the management of early-stage BCa.