Breast Cancer Biomarkers Before and After Neoadjuvant Chemotherapy: Does Repeat Testing Impact Therapeutic Management?

In patients treated with neoadjuvant chemotherapy (NAC), there is no consensus on retesting biomarkers within the excision specimen. Our aim was to investigate the clinical relevance of biomarker changes post-NAC at a large tertiary medical center. A retrospective search was performed to identify cases from 2012–2015 with needle biopsy confirmed invasive breast carcinoma treated with NAC and subsequent excision containing residual invasive tumor. Biomarkers (estrogen receptor (ER), progesterone receptor (PR), and HER2/neu (HER2)) were performed on all pre-NAC biopsies. 154 NAC treated cases were identified in which 83 (54%) had repeat testing of at least 1 biomarker on the surgical specimen. 30% of repeated cases (25/83) demonstrated changes in pre-NAC biopsy vs post-NAC resection biomarker status. There was no impact of age or grade biomarker status changes. Tumors that were triple negative at biopsy were more likely to remain triple negative. Clinically relevant changes were identified including 1. ER negative to ER positive, 3% (2/75), 2. PR negative to PR positive with ER negative both pre- and post-NAC, 3% (2/73) and 3. HER2 negative to positive, 1% (1/77). 4 of 5 of the changes led to modifications of the adjuvant treatment regimen, including the addition of adjuvant tamoxifen, anastrazole, or trastuzumab. In summary, post-NAC biomarker repeat testing in breast cancer patients impacts therapeutic management in a small subset of patients and therefore repeat testing may be considered for patients that are hormone receptor and/or HER2 negative prior to NAC.