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OA06 - Prognostic & Predictive Biomarkers (ID 452)
- Event: WCLC 2016
- Type: Oral Session
- Track: Biology/Pathology
- Presentations: 1
OA06.01 - Clinical Utility of Circulating Tumor DNA (ctDNA) Analysis by Digital next Generation Sequencing of over 5,000 Advanced NSCLC Patients (ID 6096)
14:20 - 15:50 | Author(s): A. Talasaz
Detection of actionable genomic alterations is now required for NCCN guideline-compliant work-up of NSCLC adenocarcinoma. Next-generation sequencing (NGS) of ctDNA, if sufficiently sensitive and specific, could provide a non-invasive, comprehensive genotyping platform relevant to clinical decision-making when tissue is insufficient or at time of progression on targeted therapies.
A highly accurate, deep-coverage (15,000x) ctDNA plasma NGS test targeting 54-70 genes (Guardant360) was used to genotype 5,206 advanced-stage NSCLC patients accrued between 6/2014 – 4/2016. The frequency and distribution of somatic alterations in key genes were compared to those described in TCGA (Pearson and Spearman correlations). The clinical impact of ctDNA testing was evaluated by identification of resistance mechanisms emergent at progression on targeted therapies, and through analysis of additional driver mutations detected by ctDNA at baseline in 362 consecutive NSCLC patients with tissue mutation data available. The positive predictive value (PPV) of ctDNA sequencing was assessed in 229 patients with known tumor driver alterations.
ctDNA alterations were detected in 86% of cases; EGFR mutations in 25%, KRAS mutations in 17%, MET amplification in 4%, BRAF mutations in 3% and other rare but potentially actionable alterations in 9%. Mutation patterns among driver oncogenes were highly consistent with those from TCGA (Pearson r=0.92, 0.99, 0.99 for EGFR, KRAS, and fusion breakpoint location). PPV of ctDNA-detected variants was 100% for EGFR[L858R], 98% for EGFR[E19del], 96% for ALK, RET, or ROS1 fusions, and 100% for KRAS[G12/G13/Q61] mutations. In 362 cases with tissue information available, 63% (229/362) were tissue quantity-insufficient or undergenotyped (QNS/UG). ctDNA analysis identified driver mutations in 51 of the 229 QNS/UG cases, a 38% increase in detection rate over tissue alone. Among 1,111 EGFR-mutant cases, resistance mutations were identified at progression at frequencies consistent with published literature: EGFR[T790M] 47%, MET amp 5%, ERBB2 amp 5%, FGFR3 fusions 0.4%, ALK/other fusions 1%, BRAF mutations 1.8%, PTEN inactivation 2.5%, NF1 inactivation 3%, RB1 inactivation 3%, KRAS mutations 1.9%. In 143 consecutive NSCLC patients with detailed follow-up and serial analysis seen at the UC Davis Cancer Center, informative driver mutations were observed in 48 (34%).
This series represents the largest NSCLC ctDNA study to date. Genotypic patterns of truncal mutations were highly consistent with TCGA in terms of frequency and distribution. At baseline, ctDNA augmented tissue analysis by identifying additional, actionable mutations when tissue was QNS/UG. ctDNA NGS conducted at progression identified emergent resistance mutations that could inform subsequent courses of therapy.
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P2.03b - Poster Session with Presenters Present (ID 465)
- Event: WCLC 2016
- Type: Poster Presenters Present
- Track: Advanced NSCLC
- Presentations: 1
- Coordinates: 12/06/2016, 14:30 - 15:45, Hall B (Poster Area)
P2.03b-023 - Circulating Tumor DNA (ctDNA)-Based Genomic Profiling of Known Cancer Genes in Lung Squamous Cell Carcinoma (LUSC) (ID 5393)
14:30 - 15:45 | Author(s): A. Talasaz
Next-generation sequencing (NGS) of ctDNA is increasingly used for non-invasive genomic profiling of human cancers. However, studies to date have not detailed the ctDNA genomic landscape in LUSC.
From June 2014 to June 2016, ctDNA from 467 patients with stage 3 or 4 (AJCC 7[th] edition) LUSC (60% male, 40% female; median age of 69 [range 27-96]) were tested with Guardant 360[TM], a ctDNA NGS assay that detects single nucleotide variants (SNVs) of 54-70 cancer genes and certain copy number amplifications (CNAs), indels, and fusions. The median time between diagnosis and ctDNA testing was 238 days. Somatic alterations were compared with those in the 2016 LUSC TCGA dataset.
426 patients (92.2%) had at least one somatic alteration detected. The most commonly observed SNVs (> 5% frequency) were TP53 (64.8%), PIK3CA (7.8%), CDKN2A (6.1%), and KRAS (5.9%). Frequencies of SNVs known to be significant in LUSC correlated well between our cohort and the TCGA (Spearman r = 0.93) but were generally lower in our cohort (Table 1). Several of our most frequently observed CNAs are strongly associated with LUSC (EGFR, CDK6, MYC, ERBB2, PDGFRA, KIT, CCND1). In addition, MET exon 14 skipping (1.3%), EGFR exon 19 deletion (1.9%), EGFR exon 20 insertion (0.5%), ERBB2 exon 20 insertion (0.3%) and EML4-ALK fusion (0.7%) were detected. These alterations have rarely been reported in LUSC.
Patterns of SNVs and CNAs in LUSC obtained by ctDNA profiling are largely consistent with those from TCGA tissue profiling, although the frequency of key SNVs is lower. The presence of actionable alterations atypical for LUSC in 4.7% of this clinical cohort may represent underappreciated treatment options. Further investigation is warranted to evaluate whether these findings reflect a distinct mutational landscape in heavily treated advanced disease (which is under-represented in the TCGA) and/or challenges in histopathological classification. Figure 1