Abstract 2408: A novel multiplex droplet digital PCR approach to KRAS mutation detection in circulating tumor DNA

Microdroplet digital PCR can be used to detect low frequency mutations in oncogene-driven lung cancer. Detection of circulating tumour DNA in plasma can be limited by paucity of material, particularly during response to anti-cancer therapy. The range of KRASpoint mutations observed in NSCLC necessitates a multiplex approach for efficient mutation detection in circulating DNA. We designed and optimised 3 droplet digital PCR multiplex assays investigating 9 different KRASmutations using PrimePCR™ ddPCR™ Mutation Assays and the Bio-Rad QX100 system. DNA was extracted from FFPE tissue and plasma from patients with advanced lung adenocarcinoma and was analysed to assess for the presence of these KRASactivating mutations. Multiple sub-clonal KRASmutant populations were detectable in both tissue and circulating tumour DNA at low frequency (up to 0.1%). Similar KRASallele frequency was observed using multiplex or duplex assays (r2 = 0.99). Sub-clonal population representation varied over the disease course. Multiplex microdroplet digital PCR assays can be adapted to be used to efficiently identify tissue and circulating KRASmutations in advanced lung adenocarcinoma. Variation in sub-clonal populations between tissue and plasma, and at different time points over the disease course, illustrates the potential use of circulating DNA analysis as a more readily accessible, non-invasive and accurate representation of the molecular profile of NSCLC throughout treatment. Citation Format: Alexandra Pender, Isaac Garcia-Murillas, Sareena Rana, David Gonzalez de Castro, Nicholas Turner, Sanjay Popat, Julian Downward. A novel multiplex droplet digital PCR approach to KRASmutation detection in circulating tumor DNA. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2408. doi:10.1158/1538-7445.AM2015-2408