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.