Five-Fraction Ablative RT + Endocrine Therapy Achieves 53% pCR, Skips Surgery in Stage I HR+ Breast Cancer

A single-arm Phase II trial (NCT02945579) enrolled 20 women ≥ 50 y with unicentric, stage I HR+/HER2- tumors (Oncotype ≤25). After three months of endocrine therapy and hypofractionated ablative radiotherapy (37.5 Gy/5 fx, every other day), vacuum-assisted biopsies at 6–12 mo showed pathologic CR in 10/19 (52.6%) and near-CR in another 7/19 (36.8%); pCR rate rose from 45% at 6 mo to 63% at 12 mo. Only 7 patients required surgery, and among the 12 who avoided it, no local recurrences have emerged at a median 26 mo. By contrast, neoadjuvant endocrine therapy alone rarely tops 10% pCR in ER+ disease, underscoring the boost from ablative RT.

https://aacrjournals.org/clincancerres/article/31/12_Supplement/PS6-04/753943/Abstract-PS6-04-Eliminating-breast-surgery-for