WTP8.12 Measurement of a panel of biological markers in breast cancer, a comparison between core needle biopsy and surgical excision samples

Abstract

Abstract Aims ER, PR and HER2 are routinely measured in breast cancer in clinical practice. Numerous other biomarkers exist which are only utilised in a research setting, but may have a potential role in breast cancer. The majority of research in breast cancer is conducted in surgical excision (SE) specimens due to the availability of tissue; however, it is important markers can be measured in core needle biopsy (CNB) samples in patients undergoing neoadjuvant or non-operative treatment. Methods A panel of 15 biomarkers was measured in 202 CNB and paired SE samples in a series of older women with primary breast cancer using immunohistochemistry and H-scores: ER, PR, EGFR, HER2, HER3, HER4, VEGF, p53, BRCA1, LKB1, Ki67, BCL2, CK5/6, CK 7/8, MUC1. Concordance rates were calculated between positive/negative cut-offs for each marker measured in the two samples. Results The percentage concordance rates between positive/negative cut-offs were >60% for ER, PR, EGFR, HER2, VEGF, p53, Ki67, BCL2, CK 7/8, MUC1 and <45% for HER3, HER4, CK 5/6, BRCA1 and LKB1. In general, cases were more likely to be positive in the SE sample. This could suggest SE result is an overestimation of the true value and CNB is more accurate, or at least not likely to overestimate. Conclusions The biomarkers most frequently studied in breast cancer (ER, PR, EGFR, HER2, VEGF, p53, Ki67) did show good concordance between SE and CNB samples. This may suggest that for markers less frequently studied, there is disagreement with interpretation of staining, leading to greater variation.