How Effective is Neoadjuvant Endocrine Therapy (NET) in Downstaging the Axilla and Achieving Breast-Conserving Surgery?
We reported nodal and breast downstaging rates with NET, and compared axillary response rates following NET and neoadjuvant chemotherapy (NAC).MethodsConsecutive stage I –III breast cancer patients treated with NET and surgery from January 2009 to December 2019 were identified from a prospectively maintained database. Nodal pCR rates were compared between biopsy-proven node-positive patients treated with NET, and HR+/HER2- patients treated with NAC from November 2 013 to July 2019.Results127 cancers treated with NET and 338 with NAC were included. NET recipients were older, more likely to have lobular and lower-grade tumors, and higher HR expression. With NET, the nodal pCR rate was 11% (4/38) of biopsy-proven cases, and the breast pCR rate was 1.6% (2/126). Nodal-dowstaging rates with NET and NAC were not significantly different (11% vs 18%;P = 0.37). Patients achieving nodal pCR with NET versus NAC were older (median age 70 vs 50,P = 0.004) and had greater progesterone receptor (PR) expression (85% vs 13%,P = 0.031), respectively. Of patients not candidates for BCS due to a large tumor relative to breast size, 36/47 (77%) became BCS-eligible with NET (median PR expression 55% vs 5% in those remaining ineligible,P