Role of Tumor Subtypes in Response to Neoadjuvant Chemotherapy in Non-metastatic Breast Cancer.

Background: Neoadjuvant chemotherapy (NAC) is an integral part of breast cancer treatment. Determination of the factors that can distinguish patients who will have best response to NAC is invaluable. In this study, we aimed to elucidate the factors influencing patient response to NAC.

Methods: We retrospectively collected data of female patients with non-metastatic breast cancer that had received NAC followed by surgery, admitted to Imam Khomeini hospital between 2015-2019. We investigated the association between various tumor and patients' characteristics with pathologic complete response (PCR).

Results: Overall data of 205 female patients were collected. PCR was observed in 27.6% of cases. PCR rate in luminal A, luminal B, HER2 enriched, and TNB tumors was reported in 11.1%, 30.2%, 35.7%, and 36.4% of patients respectively (=0.27). In patients with luminal B tumors, PCR was more prevalent in patients with positive HER2 only (=0.006). In our study factors which was significantly associated with PCR were: tumor grade, progesterone receptor (PR) status, and HER2 status. In the multiple regression model, positive PR in the tumor lowered the odds of pathologic response 3.6 times (=0.004).

Conclusion: In our study, tumor grade, PR status, and HER2 status was associated with response to NAC. PCR was more prevalent in non-luminal tumors; however, PCR rate in luminal B patients-especially those with HER2 positive status- was slightly less than non-luminals.