Potential benefits of neoadjuvant chemotherapy in clinically node-positive luminal subtype⁻ breast cancer

Purpose: 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. Methods: 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. Results: 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 (p = 0.836 and p = 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. Conclusion: 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.