Discordances in ER, PR and HER2 receptors after neoadjuvant chemotherapy in breast cancer

Neoadjuvant chemotherapy (NAC) for breast cancer is evolving and subsequent adjuvant systemic treatment is mainly based on the presence of the Estrogen (ER) receptor, Progesterone (PR) receptor and Human Epidermal growth factor Receptor 2 (HER2) status on the core needle biopsy prior to treatment. It is not well known whether these biomarkers change after NAC, requiring a change in further adjuvant systemic treatment. A review of the literature (PubMed search) revealed 32 relevant studies that investigated the concordance of the hormone receptors (ER and/or PR) and HER2 after NAC with or without trastuzumab. Discordance of the hormone receptor status was reported in four out of eight studies in 8-33% of the patients. About half of the studies that tested the ER and PR receptor status separately reported discordances of 2.5-17% and 5.9-51.7% respectively. Studies that concluded that ER and/or PR receptor remained stable after NAC were performed with evidently lower number of patients compared to studies that reported a change. Good concordance of the HER2 amplification tested with FISH was reported, although the HER2 expression measured with immunohistochemistry was more discordant. A switch to a negative HER2 receptor in up to 43% of the patients was reported when NAC was combined with trastuzumab. Until more comparable studies are being published, retesting the receptor status of the residual tumor after NAC should be considered in order to improve future tailored adjuvant therapies.