Abstract 2217: Concordance of PIK3CA mutations in hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer: A systematic literature review

Abstract

Abstract Introduction: This systematic literature review sought to determine the concordance of PIK3CA mutations in hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (mBC) patients. Methods: A comprehensive search of PubMed/MEDLINE, EMBASE, Cochrane Central, and select conference abstracts was performed by two independent researchers that included, but was not limited to, keywords: “breast neoplasm,” “PIK3CA protein,” “hormone receptor positive,” and “metastases.” Databases were searched for English-language publications in HR+, HER2- mBC published between January 1993 through August 2017. Studies were included if results reported were specific to patients with HR+, HER2- mBC and reported data comparing PIK3CA mutations from liquid biopsies versus tumor biopsies or primary tumor samples versus metastatic lesion samples. Concordance was assessed between tissue samples (mutations found in primary tumors versus those from metastatic lesions) and between biopsy methods (i.e., tumor biopsy versus liquid biopsy) when the assessment was done at a variety of time points including time of initial diagnosis and time of diagnosis at disease progression. Content analysis was employed to quantify collected data elements. Results: Of 558 studies included for full-text review, four met inclusion criteria (number of patient samples [n]=358). One study (n = 9) found the concordance between the mutation status of primary breast tumors to the mutation status of metastatic lesions to be 100%. Three studies (n = 47; n = 55; n = 247) determined the concordance of PIK3CA mutations between tumor biopsies and liquid biopsies with concordance ranging from 70.4% to 94%. One study found that the concordance of circulating tumor DNA (ctDNA) against tumor biopsy was higher among metastatic lesions only (81.6%) relative to using all tumor samples (either primary or metastatic lesions) (70.4%). Conclusions: Available evidence suggested high level of concordance across sampling methods as well as across time. However, additional evidence is needed to increase study generalizability as well as to assess other possible confounding factors, such as differential timing between tumor and liquid biopsies. Citation Format: Alejandra Aguilar, Joni Dean, Elizabeth Anderson, Lea Mollon, Lisa Davis, Terri Warholak, Ayal Aizer, Emma Platt, Aditya Bardiya, Derek Tang. Concordance of PIK3CA mutations in hormone receptor-positive, human epidermal growth factor receptor 2-negative breast cancer: A systematic literature review [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2217.