Axillary Management after Neoadjuvant Endocrine Therapy (NET)

In patients with hormone receptor-positive (HR⁺), HER2-negative breast cancer, there is a lack of data available to define optimal axillary management strategies after neoadjuvant endocrine therapy (NET).

We performed a retrospective review of patients with clinical stage I-III, HR⁺ breast cancer who received > 90 days of NET at a single comprehensive cancer center between 2004 and 2024.

A total of 230 patients were included; 120 (52.2%) were clinically node-negative (cN0), while 110 (47.8%) were clinically node-positive (cN+). In the cN+ group, 7.3% (8/110) had a nodal pathologic complete response (pCR). In total, 76.4% (84/110) in the cN+ group underwent axillary lymph node dissection (ALND) as the initial axillary procedure, and 90.9% (100/110) underwent ALND overall. In total, 98.3% (118/120) with cN0 disease underwent sentinel lymph node dissection (SLND), and 28 (23.7%) had positive nodes. A total of 64.3% (18/28) of cN0 patients with a positive SLN underwent ALND. There were four local-regional recurrences (LRR) in the entire cohort, yielding a 5-year LRR rate of 2.2%, and it did not differ between cN0 and cN+ (2.0% versus 2.2%, p >0.05). The distant recurrence rate was higher in cN+ compared with the cN0 group (15.0% versus 6.9%, p = 0.03). The 5-year overall survival (OS) was 79.5% for the entire cohort and was higher for cN0 compared with cN+ patients (88.4% versus 69.7%, p = 0.004).

The 5-year LRR rate was extremely low for the entire cohort, suggesting that NET is an oncologically safe strategy for patients with HR⁺ disease even in the setting of large tumors and positive lymph nodes.