Relationship of Neoadjuvant Chemotherapy Efficacy with Histopathologic Molecular Subtypes in Breast Cancer Patients

Introduction: Breast cancer is the most common malignancy in women, and it is the second leading cause of malignancy-related mortality in women after lung cancer. Locally advanced breast cancer is a clinically heterogeneous group with a broad spectrum. Neoadjuvant chemotherapy (NAC) is the standard treatment at this stage. The present study aimed to evaluate the efficacy of NAC in terms of histopathologic molecular subtypes. Methods: The study included 183 patients receiving NAC. Patients were studied in three groups: Luminal tumors, human epidermal growth factor receptor-2 (HER-2)-positive tumors, and triple-negative tumors based on the expressed receptor status. In our retrospective review, we only examined pathological complete response (pCR) based on breast tumor shrinkage before and after chemotherapy. In this study, we evaluated factors affecting pathologic complete response in patients receiving NAC. Results: According to breast cancer subtypes based on biopsy results, pCR developed in 8 of 20 patients with triple-negative tumors (40%), 24 of 61 patients with HER-2-positive tumors (39.3%), and 22 of 102 patients with luminal tumors (21.5%) (p=0.030). The pCR rate was available in 5 of 40 patients with lymphovascular invasion (LVI) (12.5%) and 49 of 143 patients without LVI (34.2%) (p=0.008). pCR was available in 1 of 16 patients with perineural invasion (PNI) (6.6%) and 53 of 168 patients without PNI (31.5%) (p=0.043). PCR was available in 2 of 25 patients with extracapsular lymph node invasion (8%) and in 52 of 158 patients without extracapsular lymph Conclusion: The NAC pCR rate of hormone-positive tumors was lower than that of hormone-negative tumors in breast cancer. This finding was related to the biological response of the tumor in heterogeneous breast cancer.