Clinical implications of receptor conversions in breast cancer patients who have undergone neoadjuvant chemotherapy

In this study, we aimed to determine the incidence of receptor conversions after neoadjuvant chemotherapy (NAC) for breast cancer and assess the rate at which receptor conversion leads to changes in adjuvant therapy regimens.

We performed a retrospective review of female breast cancer patients treated with NAC at an academic breast center between January 2017 and October 2021. Patients with residual disease on surgical pathology and complete receptor status information for both pre-NAC and post-NAC specimens were included. Incidence of receptor conversions, defined as a change in at least one hormone receptor (HR) or HER2 status compared to preoperative specimens, was tabulated, and adjuvant therapy modalities were reviewed. Factors associated with receptor conversion were analyzed using chi-square tests and a binary logistic regression.

Of the 240 patients with residual disease after NAC, 126 (52.5%) had receptor testing repeated. After NAC, 37 specimens (29%) had a receptor conversion. Receptor conversion resulted in the addition or removal of an adjuvant therapy in 8 patients (6%), indicating a number needed to screen of 16. Prior history of cancer, receipt of initial biopsy at an outside site, HR-positive tumors, and a pathologic stage of II or lower were factors associated with receptor conversions.

HR and HER2 expression profiles frequently change after NAC and drive adjustments in adjuvant therapy regimens. Repeat testing of HR and HER2 expression should be considered in patients who receive NAC, especially in patients with early stage, HR-positive tumors whose initial biopsies were performed externally.