Impact of Immunohistochemistry-Based Molecular Subtype on Chemosensitivity and Survival in Patients with Breast Cancer Following Neoadjuvant Chemotherapy

Purpose: Pathologic complete response (pCR) has been suggested as a surrogate prognostic indicator in breast cancer patients treated with neoadjuvant chemotherapy. We assessed whether the likelihood of pCR and survival is associated with the immunohistochemistry-based molecular subtypes. Methods: We retrospectively analyzed the records of 276 patients with breast cancer who received neoadjuvant chemotherapy between January 2000 and January 2010. Patients were classified into four molecular subtypes based on the immunohistochemistry profiles of estrogen receptor, progesterone receptor, and HER2/neu. Logistic regression was used to analyze variables associated with pCR. Results: The pCR was achieved in 45 patients (16.3%). The triple negative subtype was an independent predictive factor for pCR (odds ratio, 3.21; 95% confidence interval, 1.20-8.56; p=0.020), and the ERBB-2 subtype showed a trend for higher pCR rates (odds ratio, 3.03; 95% confidence interval, 0.93-9.89; p=0.067) compared with the luminal A subtype. In 99 patients with HER2/neu-positive breast cancer, pCR rates were higher in those who received trastuzumab (31.7%) than those treated with conventional chemotherapy regimens (17.2%, p=0.023). The pCR was significantly associated with prolonged progression-free survival (p=0.008). The triple negative subgroup had shorter progression-free survival (p=0.001) and overall survival (p=0.001) than the other subgroups. Conclusion: We demonstrated that the triple negative and ERBB-2 subtypes are more likely to obtain pCR when neoadjuvant chemotherapy is given, compared to the luminal A subtype. Despite the high pCR rate, the triple negative subtype showed worse survival outcomes, paradoxically, primarily due to patients who had residual disease.