Abstract P5-08-35: Correlation of predictive markers in invasive breast carcinoma in core and excision specimens: A retrospective review

Abstract

Abstract Background: Testing of biomarkers in biopsies is a critical driver of determining therapy in patients diagnosed with invasive breast cancer. In the past, open surgical biopsy was considered to be the gold standard, but has been supplanted by the less invasive core needle biopsy. It is therefore imperative to know if such biopsies are representative of disease existing within the entirety of the tumor. This is especially the case now that neoadjuvant therapy is offered to patients with early stage tumor prior to surgical excision. In order to confirm that core biopsies are sufficient to serve as the launch point for treatment decision, we have conducted a retrospective review to compare the biomarker results of core biopsies with their corresponding excisional specimens. Previous studies have contained a smaller sample size, thus this is the largest single-site study of its kind. Methods: Data from patients with invasive breast cancer diagnosed between 2006 and 2013 have been retrospectively studied. Results for estrogen receptor (ER), progesterone receptor (PR) and Her2 status were analyzed. When the core biopsy and excisional specimens are either both "positive" or both "negative," the pair is considered to be "concordant." Otherwise, the pair is categorized as "discordant." As per the current ASCO/CAP guideline, hormone receptor status (estrogen and progesterone receptors) is considered positive if there were at least 1% tumor cells positive for either ER or PR. Both IHC and FISH concordance are evaluated for Her2 status. Patients who received neoadjuvant therapy of any kind were excluded from this study. Results: A total of 571 pairs of data totaling 1142 samples were analyzed in this study. Concordance for ER status is 97%, and for PR status is 92%. Concordance for hormone receptor status (when results of ER and PR are combined) between core biopsy and excision is 99%. Concordance for Her2 status, using FISH as the gold standard is 99%. Discussion: Typically, tumors that are ER+ are often also PR+. Nevertheless, they are often treated the same with hormonal therapy whether ER+PR+, ER+PR-, or, less commonly, ER-PR+. Almost all laboratories perform both ER and PR as a standard testing protocol for all breast carcinomas. Therefore, the lower concordance rate for only PR status without taking into consideration ER result is less meaningful. This study shows very high concordance rates for hormone receptor and Her2 status between core needle biopsy and excisional specimens, reiterating that treatment of invasive breast cancers based on the marker results obtained from core needle biopsies is appropriate. Citation Format: Music J, Sahoo S. Correlation of predictive markers in invasive breast carcinoma in core and excision specimens: A retrospective review. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-08-35.