Retesting of oestrogen receptor, progesterone receptor and HER2 status of invasive carcinoma of the breast after neoadjuvant chemotherapy

AimsThere is no consensus on whether oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) status should be assessed after neoadjuvant chemotherapy. This study assessed the frequency of changes in ER, PR and HER2 status after neoadjuvant chemotherapy.Methods and resultsOf 353 patients who had neoadjuvant chemotherapy and anti-HER2 treatment, receptors were assessed in 185 residual carcinomas. Eight per cent of carcinomas that were ER-negative in the core biopsy were ER-positive in the excision compared with 1.5% of controls. All were HER2-positive in the core biopsy and 23% were HER2-negative in the excision compared with 0% of controls. Controls were cases tested in the core biopsy and subsequent surgical resection with no neoadjuvant treatment. Of 589 patients who had neoadjuvant chemotherapy alone, receptors were assessed in 495 residual carcinomas. Six per cent of carcinomas that were ER-negative in the core biopsy were ER-positive in the excision (mainly ER-low positive) compared with 1.5% of controls. All were HER2-negative in the core biopsy and 6% were HER2-positive in the excision (mainly immunohistochemistry score 2+ and HER2 gene amplified) compared with 2% of controls.ConclusionsNegative to positive changes in receptor status after neoadjuvant chemotherapy are infrequent and the positive result in the excision is often weakly positive. These results imply that repeat assessment after neoadjuvant chemotherapy and surgery could influence the subsequent treatment in a small proportion of patients.