Predictors of Axillary Complete Pathologic response in Hormone Receptor Positive, HER2 Negative Clinically...

Neoadjuvant therapy can downstage the axilla, reducing the need for an axillary dissection. In addition, obtaining a complete pathologic response in the axilla is associated with a better 10 year overall survival. Our institution previously reported axillary response rates in hormone positive, human epidermal growth factor receptor 2 (HER2) negative, clinically node-positive breast cancer patients undergoing neoadjuvant therapy in a small cohort of patients. The cohort however was too small for a deeper dive into potential predictors of response. In this current study, we sought to expand this cohort of patients until 2022 almost doubling the number of patients to better evaluate for potential predictors of response.

A single-institution retrospective cohort study included hormone receptor-positive, HER2 negative, clinically node-positive breast cancer patients treated with neoadjuvant therapy, either endocrine or chemotherapy, between January 2011 to December 2022. The data was divided in patients with cPR and no cPR in the axilla. The primary outcome was to identify demographic and clinicopathologic parameters that co-related to cPR in the axilla. Chi-square test or Fisher's exact test for categorical variables and t-test for continuous variables were performed. Logistic regression analysis was performed to assess clinical factors associated with the number of complications.

Two hundred breast cancer patients met the inclusion criteria. They were divided into two cohorts: patients with axillary cPR rate 12% (n = 24) and no axillary cPR 88% (n = 176). The mean age was 52.17 [standard deviation 11.5]. The demographic profile of patients, tumor characteristics, and treatment is described in Table 1. Amongst the patients who underwent genomic profile (n = 25), 76% (n = 19) had Mammprint done, while 24% (n = 6) had Oncotype. There were 2 patients with cPR in the axilla who had mammaprint performed, both of which were found to be high risk. For patients who underwent chemotherapy, approximately 13.6% achieved axillary cPR. For patients who underwent hormone therapy, approximately 6.5% achieved axillary cPR (p = 0.29). A significantly higher axillary cPR rate was identified in patients with clinical stage II at diagnosis (14/70, 20%) compared with stage III (10/128, 7.8%; p = 0.013). Patients with axillary cPR had on fewer lymph nodes removed at the time of surgery, 8 vs. 16 (p = 0.001).

An axillary cPR in hormone receptor-positive, HER2 negative, clinically node-positive breast cancer patients was higher in those patients with a lower clinical stage (stage II). Patients with a cPR were able to avoid an axillary dissection. A larger cohort of patients is necessary to define more possible predictors of axillary response rate to neoadjuvant therapy.