Abstract 4264: Liquid biopsy and FFPE tissue based somatic BRCA1/2 variant screening in breast and ovarian cancer

Abstract

Abstract Next generation sequencing (NGS) has widened its use since it provides highly precise and accurate genetic testing with reasonable costs in tumor genetic profiling from somatic materials such as FFPE (formalin fixed paraffin embedded) tissue and liquid biopsy [circulating cell free DNA (ccfDNA)]. It has a high value in differentiating treatment strategies especially in BRCA1/2 genomic profiling in breast and ovarian cancer. However, somatic BRCA1/2 testing still remains unclear algorithm versus germ-line testing approved in human genetics for many decades. Thus, we sum up our testing results in relation with clinical diagnosis. FFPE samples from 89 and 74 liquid biopsy samples from breast and/or ovarian cancer patients were collected and sequenced via the GeneReader NGS system for BRCA1 and BRCA2 genes. QCI-Analyze and QCI-Interpret bioinformatics tools were used for bioinformatics analyses. We detected 56 actionable variants in 48 patients (29.5%) out of 163 patients. The 46.4% (nvariant=26) of the mutations were detected in BRCA1 gene while 53.6% (nvariant=30) of them were in BRCA2 gene. The allele frequencies vary from 1.43% to 100% with an average of 43% in 89 FFPE tissue samples with the positivity rates of 30% (nsample=27) while the rate is 28.4% (nsample=21) in 74 liquid biopsy samples. Interestingly, 8 patients had more than one actionable variant and 5 of them had mutations both in BRCA1 and BRCA2 genes. To sum up, genetic testing for targeted treatments has become first-line clinical testing in cancer and taken its place in international guidelines. Thus, somatic testing to profile BRCA genes should be considered in breast and ovarian cancer algorithm since 5% percent of the patients additionally carry somatic actionable mutation with regarding 15% positivity in germ-line BRCA1/2 studies. Citation Format: Ibrahim Boga, Ozge Sonmezler, Atil Bisgin. Liquid biopsy and FFPE tissue based somatic BRCA1/2 variant screening in breast and ovarian cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4264.