Potential Benefits of Neoadjuvant Chemotherapy in Clinically Node-Positive Luminal Subtype - Breast Cancer

Neoadjuvant chemotherapy (NAC) is less effective for luminal breast cancer because luminal breast cancer has a lower rate of pathological complete response (pCR) after NAC than human epidermal growth factor receptor 2 (HER2)-type and triple-negative breast cancer (TNBC). We investigated the efficacy of NAC and the predictive factors of a better response in luminal breast cancer. Between 2010 and 2016, we retrieved data of 244 patients with clinically node-positive breast cancer who were treated with NAC followed by surgery from a prospectively collected database. We classified breast cancer into luminal HER2 and non-luminal HER2 breast cancer (luminal HER2 , HER2 , and TNBC types). We analyzed each subtype with respect to surgical outcomes, response to NAC, and determined variables associated with surgical outcomes and response in patients with luminal HER2 breast cancer. The total, breast, and axillary pCR rates were significantly lower in 114 patients with luminal HER2 breast cancer than in those with other subtypes (7.9%, 12.3%, and 22.8%, respectively). However, breast-conserving surgery (BCS) conversion and tumor response rates did not significantly differ between patients with luminal HER2 and those with non-luminal HER2 breast cancer ( = 0.836 and = 0.180, respectively). In the multivariate analysis, high tumor response rate (≥ 46.4%) was significantly associated with an increased BCS conversion rate. In the subgroup analysis of luminal HER2 breast cancer, the multivariate analysis showed that higher Ki67 expression and axilla pCR and BCS conversion rates were significantly associated with tumor response to NAC. Despite the low pCR rate, the tumor response and BCS conversion rates after NAC of luminal HER2 breast cancer were similar to those of other subtypes. NAC has the potential benefit of reducing the size of breast cancer, thereby increasing the BCS conversion rate in luminal HER2 breast cancer.