Evaluation of Pathologic Complete Response (pCR) to Neoadjuvant Chemotherapy in Iranian Breast Cancer Patients with Estrogen Receptor Positive and HER2 Negative and Impact of Predicting Variables on PCR

Objective: The pathologic complete response (pCR) in the breast and axillary lymph node after neoadjuvant chemotherapy (NAC) would improve outcomes and it is used as a surrogate marker for survival. Our objective was to evaluate the breast and nodal pCR in breast cancer patients with estrogen receptor-positive (ER) and HER2 negative subtypes. Meanwhile, we sought to examine the impact of predicting factors on the rate of pCR.

Materials And Methods: In this multicenter retrospective study, medical records data of 314 women with ER+/HER2- breast cancer subtype who received neoadjuvant chemotherapy was extracted from oncology centers' data between 2011 and 2018. Breast and axillary lymph node pCR were assessed. Meanwhile, receiver operating characteristic (ROC) curve analysis was performed to assess the predictive value for proliferative index (Ki-67%) expression.

Results: Breast pCR was seen in 25.2% (n=79) of the 314 cancer patients and partial response was seen in 47.8% (n=150), too. Nodal pCR was reported in 30.9% (n=97) of the 249 node-positive patients. The overall pCR (both breast & node) was observed in 14.6 % (n=46) of the 272 patients in which the data of breast and nodal were available. We identified 22.5% as the best cut-off value for ki-67 expression in predicting complete response to NAC.

Conclusion: The pCR rate after NAC in ER+/HER2- subtypes of breast cancer is low. Therefore, the optimal therapy for these patients should be further investigated.