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A. Lawson
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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
- Moderators:
- Coordinates: 12/06/2016, 14:30 - 15:45, Hall B (Poster Area)
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P2.03b-093 - Validation and Performance of a Standardized ctDNA NGS Assay across Two Laboratories (ID 6389)
14:30 - 14:30 | Author(s): A. Lawson
- Abstract
Background:
Molecular profiling of tumors using circulating tumor DNA (ctDNA) in the blood of cancer patients, as a liquid biopsy, is rapidly becoming established as a useful source of information to aid clinical decision-making when a solid tumor biopsy is not available, or is limited in amount or quality. DNA alterations are often found in a small fraction of the total cell free DNA in plasma, and their detection requires specially designed assays that are sensitive and reproducible. Individual hotspot mutations can be assayed using technologies such as droplet/digital PCR, but multiplexing such assays is limited by the small amount of clinical material. This can be addressed by assays based on next generation sequencing (NGS), to create sensitive panels for ctDNA analysis. For clinical application, it is essential that such NGS assays be standardized and reproducible, both intra-and inter-laboratory. Standardization for tissue-based NGS assays has only recently been implemented, after much discussion. We describe a strategy for validation and standardization of a high sensitivity NGS-based ctDNA assay between two laboratories, based in the US and UK.
Methods:
The enhanced TAm-Seq[®] assay (eTAm-Seq™) uses efficient library preparations and bespoke algorithms to identify cancer mutations within a panel of 34 genes, covering cancer hotspots as well as entire coding regions of selected genes. To ensure this complex process is standardised and controlled, a high level ISO and CLIA quality management system is implemented. To perform analytical validation of this assay, we used reference standards and plasma controls to demonstrate the sensitivity, specificity and quantitative accuracy of this ctDNA analysis platform.
Results:
We compared performance of the assay between two laboratories, finding a high rate of concordance and reproducibility. Using DNA quantities typical of those found in up to 4ml of plasma from cancer patients, our assay provides high sensitivity for variants that are present at allele fraction 0.25% or higher in plasma, and retains substantial sensitivity at allele fractions as low as 0.1%. Standard dilution curves of well-characterized reference samples show that the accuracy of the eTAm-Seq[®] assay is predominantly limited by stochastic sampling. Analysis of plasma samples from control individuals demonstrates a low false positive rate. Additional data with associated clinical data will be presented at the meeting.
Conclusion:
Our data demonstrates eTAm-Seq[TM] assy's robustness and performance in two labs, supporting its use as a basis for clinical applications globally, allowing a high degree of standardization and comparability for molecular profiling of tumors using liquid biopsy.
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P3.02b - Poster Session with Presenters Present (ID 494)
- Event: WCLC 2016
- Type: Poster Presenters Present
- Track: Advanced NSCLC
- Presentations: 1
- Moderators:
- Coordinates: 12/07/2016, 14:30 - 15:45, Hall B (Poster Area)
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P3.02b-102 - Osimertinib Benefit in ctDNA T790M Positive, EGFR-Mutant NSCLC Patients (ID 5472)
14:30 - 14:30 | Author(s): A. Lawson
- Abstract
Background:
The third generation tyrosine kinase inhibitors (TKIs) osimertinib is approved for patients with acquired epidermal growth factor receptor (EGFR) T790M mutations in advanced non-small cell lung cancer (NSCLC) patients. New tissue biopsy to detect T790M cannot always be performed, due to the size or location of the lesions and risk of complications to the patient. As an alternative, liquid biopsies based on circulating cell-free tumor DNA (ctDNA) analysis have been described. We assess the efficacy of osimertinib in ctDNA T790M-positive, EGFR-mutant NSCLC patients with progression under first- or second-generation EGFR TKIs ineligible for tissue biopsy at progression; and the feasibility of identifying T790M mutations in ctDNA isolated from blood samples in this cohort of patients.
Methods:
ctDNA analysis using enhanced eTAm-Seq™ assay (Inivata), and enhanced version of the Tam-Seq ® assay was conducted in 48 eligible patients treated in a single center between April 2015 and April 2016. Patients determined to have T790M mutation were prescribed osimertinib (80mg daily). Objective response rate (ORR) by RECIST 1.1 criteria was centrally reviewed and correlated with (A) T790M allele fraction, (B) EGFR activating mutation allele fraction, and (C) T790M by EGFR activating mutation allele fraction ratio.
Results:
T790M status in ctDNA was assessed in 48 EGFR-mutant NSCLC patients. Median age was 65 years (range 37-83); 36 (75%) patients were women and 58% were never-smoker. EGFR mutation status was Del19 in 33 (69%) and L858R in 15 (31%) NSCLC patients. The ctDNA T790M mutation was positive in 24 out of 48 (50%) patients, and 23 out of 24 T790M-positive samples maintained the original activating EGFR mutation in ctDNA analysis. Among evaluable patients (n=16), osimertinib gave a partial response rate of 62.5% and a stable disease rate of 37.5%. Neither correlation between ctDNA T790M AF and RECIST radiological response was observed, nor with the other parameters evaluated. Of the seven cases with best response (decrease of 50% or more in size), 3 cases had T790M detected at <0.25%.
Conclusion:
Osimertinib efficacy in a real-world setting among T790M-positive tumours detected in ctDNA from liquid biopsy support the use of such liquid biopsies as a surrogate marker for T790M in tumour tissue, avoiding the need for invasive tumor biopsies for personalising treatment in lung cancer patients
