Abstract 625: The frequency of gene amplifications in cancer revealed by a droplet digital PCR (ddPCR) based pan-cancer gene panel test

Abstract The development of molecular assays designed to detect gene amplifications has largely been hampered by technical challenges such as limited DNA quantity and tumor heterogeneity, which demand methods of very high precision and sensitivity. The recent introduction of affordable digital PCR platforms, such as droplet digital PCR (ddPCR), that are capable of providing single molecule resolution of target abundances thus provides a unique opportunity to address this gap in molecular diagnostics. A ddPCR-based test was therefore developed under CLIA-CAP guidelines to determine the amplification status of 12 commonly amplified genes targeted by FDA approved drugs. Termed the Amplinome Test, this test was applied to 49 clinical samples received over a period of 6 months and compared to the results obtained from a commercially available clinical sequencing test applied that also reports copy number alterations (CNAs). An overall concordance rate of 90% (532/588 calls) was observed between the two tests across the entire gene set, 5 of which were identified as amplified. There were 56 discordant copy number amplifications between the two testing modalities. The vast majority (55/56) of discordant calls arose from gene amplifications identified by the Amplinome test, but not detected by sequencing, indicating an 11-fold increase in sensitivity in detecting amplifications. One discordant call (HER3) was identified as amplified via sequencing, but confirmed to be unamplified via FISH. At the patient level, the Amplinome test identified 5-fold more patients as having actionable amplifications in at least one of the 12 assayed genes versus clinical sequencing (29 vs. 6). Clinical management was altered in 14 of the 29 patients with an actionable CNA identified on the Amplinome test; those patients received targeted therapy directed against the amplified gene. The ddPCR-based Amplinome test thus provides a highly sensitive method for measuring gene amplifications in cancer that alters patient management, and suggests that the prevalence of actionable amplifications may be significantly underestimated by standard clinical next-generation sequencing tests. Citation Format: Austin P. So, Amy Wong, Jennifer Pecson, Girish Putcha, Gregory Jensen, Michael Lucero, Gary Stone, Jason Gillman, Pravin Mishra, David Loughmiller, Derrick S. Haslem, Lincoln Nadauld. The frequency of gene amplifications in cancer revealed by a droplet digital PCR (ddPCR) based pan-cancer gene panel test. [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 625. doi:10.1158/1538-7445.AM2015-625