Next-generation sequencing of FFPE solid tumor specimens for clinical use.

Abstract

10524 Background: As more therapies targeting genomic alterations become available, genotyping (e.g., by Sequenom) is increasingly performed in tumor types where mutational status may drive treatment choice. Next-generation sequencing (NGS) technology can expand on genotyping of individual base pairs because it can detect mutations across entire exons, copy changes and fusion genes. However, for NGS to be clinically viable, it must be made compatible with FFPE tissues and shown concordant with best current diagnostic methods. Methods: To explore a potential clinical role for NGS, we selected 120 FFPE specimens (68 NSCLC, 32 CRC, 20 melanoma) previously tested for 97 oncogenic mutations in 8 oncogenes by Sequenom, and sequenced all exons of 182 cancer genes. Genotyping and sequencing were both performed in CLIA compliant labs. DNA was extracted from 4x 10μ unstained sections from the diagnostic FFPE block, followed by library construction and hybridization capture of 3230 exons and 37 commonly rearranged introns. Average coverage of >900X uniquely-mapping reads was obtained. Sequence data were analyzed for all genomic alterations and examined for potentially actionable mutations. Results: High concordance was noted between Sequenom and NGS: 103 and 105 mutations were called by the two technologies, respectively, at mutually tested sites, with 97 mutation calls in common. Notably, mutant allele frequencies in concordant calls ranged as low as 2% by NGS, highlighting the sensitivity of detection enabled by both approaches. Furthermore, in 45/120 (38%) specimens, NGS revealed additional alterations that may confer sensitivity or resistance to approved or experimental targeted therapies and thus plausibly influence treatment decisions. These included 39 copy changes or loss-of-function variants best assayed by an NGS approach. Conclusions: Our results demonstrate technical feasibility and highlight potential benefits of comprehensive cancer gene characterization through next-generation sequencing of clinical FFPE specimens. As NGS is the most practical means to detect all classes of somatic alteration in a small, clinically relevant sample, we suggest that this type of testing will become an essential component of patient care.