The Association of Neoadjuvant Systemic Treatment on Hormone Receptor and Her2 Expression in Breast Cancer

Background: Pathological complete response (pCR) following neoadjuvantsystemic treatment(NAST) for breast cancer is associated with improvedprognosis; however, a large proportion of patients have residual disease.Oestrogen Receptor (ER) and HER2 status have been shown to affect likelihood ofachieving pCR, with ER positive tumors being more treatment resistant. Ashormone receptor status is heterogeneous within tumors, we postulated that,following NAST, ER expression would change in patients with residual disease, asthe ER negative cells within the tumor are more treatment sensitive.Methods: A retrospective case series of patients treated with NAST prior tosurgery at our institution was conducted. Information collected includeddemographic data, tumor grade, hormone receptor and HER2 status both beforeand after treatment, and pCR rates.Results: Of the 44 patients included, half achieved pCR. HER2 status(P=0.01), and subtype (P=0.008) were significantly associated with pCR. HER2positive/ER negative tumors were most likely to undergo pCR. Approximately80% of residual disease was ER positive. Higher levels of ER expression were alsoassociated with increasing residual cancer burden (RCB) class (P=0.037). Therewas no trend between change in ER or HER2 expression following NAST. Medianchange in ER expression was 80% to 90% (P= 0.89), HER2 intensity changed from3.0 to 2.2 (P=0.67) following treatment.Conclusion: Consistent with the literature, we have shown associationsbetween ER and HER2 status and PCR, and between ER expression and residualdisease burden. Our study was not able to demonstrate a significant trend inhormone and HER2 expression.

The Association of Neoadjuvant Systemic Treatment on Hormone Receptor and Her2 Expression in Breast Cancer Keywords:

HER2 , hormone status , neoadjuvant , pathological complete response , residual disease