Molecular subtypes and tumor response to neoadjuvant chemotherapy in patients with locally advanced breast cancer

Objective: Pathologic complete response (pCR) is the most predictive factor for patients with neoadjuvant chemotherapy and we investigated the rate of pCR according to molecular subtypes defined by immunohistochemical staining. Methods: Our subjects comprised 257 breast cancer patients who received 3 cycles of anthracycline/taxane-based neoadjuvant chemotherapy. The patients were classified into 4 subtypes: luminal A, luminal B, HER2 and triple negative. We analyzed the pCR rate and treatment outcome according to these subtypes. Results: Of a total of 257 patients, the pCR rate of luminal A, luminal B, HER2 and triple negative was 3.9, 5.0, 10.5 and 21.1%, respectively (p = 0.001). The 5-year disease-free survival of the pCR group (88.4%) was higher than that of the non-pCR group (65.6%), but it was not significant (p = 0.228). Among patients who have residual disease, the 5-year disease-free survival of luminal A, luminal B, HER2 and triple negative was 64.0, 65.7, 75.2 and 66.5%, respectively (p = 0.243). Triple negative and HER2 subtypes are more sensitive to neoadjuvant chemotherapy. Conclusion: To increase the pCR rate, type-specific approaches according to subtypes, such as an addition of trastuzumab, increasing the number of cycles or a novel regimen, should be considered.