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C. Swanton
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MS 05 - Tumor Heterogeneity (ID 23)
- Event: WCLC 2015
- Type: Mini Symposium
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:S. Dacic, A.G. Nicholson
- Coordinates: 9/07/2015, 14:15 - 15:45, Mile High Ballroom 1a-1f
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MS05.01 - Overview of Tumor Heterogeneity (ID 1864)
14:20 - 14:40 | Author(s): C. Swanton
- Abstract
- Presentation
Abstract:
Despite advances in genomic technologies, most advanced solid tumors remain incurable and drug resistance is almost inevitable with limited biomarkers available to personalize therapy. Two important lessons have emerged from the comprehensive genomic analyses of cancers, which may provide an explanation for difficulties that have been encountered in biomarker development. First, each tumor contains an individual assortment of multiple genomic aberrations, few of which are shared between patients with the same histopathological tumor subtype. Second, emerging evidence suggests that these anomalies appear to vary both spatially and temporally within the tumor, indicating substantial intratumor heterogeneity. Increasingly, molecular evidence suggests that intratumor heterogeneity may contribute to tumor growth through a branched (polytypic) rather than a linear pattern of tumor evolution. Branched evolutionary growth and intratumor heterogeneity results in coexisting cancer cell subclones with variegated genotypes and associated functional phenotypes that may be regionally separated within the same tumor or distinct within one biopsy and alter in dominance over time. Variegated phenotypes, resulting from intratumoral genetic heterogeneity and the emergence of new subclones at relapse, are likely to have important implications for developing novel targeted therapies and for preventing the emergence of drug resistance. Intratumor heterogeneity and tumour sampling bias, resulting from single biopsy-driven biomarker discovery and validation approaches, may also contribute to the recently reported failures in implementation of robust biomarkers in the clinical setting. Clinical trial efforts taking into account tumour heterogeneity and its relevance to lung cancer will be addressed.
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P3.01 - Poster Session/ Treatment of Advanced Diseases – NSCLC (ID 208)
- Event: WCLC 2015
- Type: Poster
- Track: Treatment of Advanced Diseases - NSCLC
- Presentations: 1
- Moderators:
- Coordinates: 9/09/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P3.01-038 - Comparing Next-Generation Sequencing (NGS) Platforms in Patients with Thoracic Tumors: Tumor Tissue vs. Circulating Cell-Free DNA from Blood (ID 1732)
09:30 - 09:30 | Author(s): C. Swanton
- Abstract
Background:
Next-generation sequencing (NGS) from tumor tissue is used to acquire comprehensive genomic information to aid clinical decision-making for cancer patients. In order to obtain sufficient tissue for tumor-based NGS, patients must often undergo repeat biopsies after diagnosis which are invasive, associated with risk and expense, and sometimes unsuccessful because of tumor size or location. Genomic information may also be obtained by analyzing cell-free DNA (cfDNA) from plasma samples, which affords the potential for NGS testing to a greater number of patients, and offers a wide variety of cancer diagnostic and surveillance applications. We sought to compare the results of tumor based-NGS with an analysis of circulating tumor cfDNA from matched plasma samples in patients with thoracic tumors (non-small cell lung cancer, small cell lung cancer and thymic malignancies) to determine concordance between the tests.
Methods:
We compared NGS results obtained from tumor tissue analyzed by Foundation One with plasma-based analysis of cfDNA using Guardant360, a 54-gene panel covering 80,000 base pairs with high sensitivity (75-85% in most solid tumors) and ultra-high specificity (>99.9999%). Guardant360 detects single nucleotide variants (SNVs), including synonymous alterations, variants of uncertain significance, and somatic point mutations, gene amplifications (CNVs), select insertions/deletions (indels) and genomic rearrangements. Because Foundation One is a 316-gene panel, concordance was defined based on the genes covered by both panels. Only patients with cancers originating in the chest were included.
Results:
Of 56 patients with Guardant360 testing performed between 6/2014 and 2/2015, 100% were successfully assayed. Eleven had matched NGS from tumor and concordance was noted in 5/11 (45%) of patients. TP53 and KRAS were commonly found in both tumor tissue and plasma cfDNA. A total of 34 patients (61%) with successful plasma-based cfDNA analysis were unable to undergo tissue-based NGS for various reasons; fourteen patients had tumor tissue sent for NGS analysis that was deemed “insufficient”, 16 had exhausted prior tumor biopsy specimen, and 4 patients were too ill to undergo a repeat biopsy. In 19 of these 34 cases where tissue NGS results were not available (56%), a genomic alternation was identified by plasma cfDNA analysis, which corresponded to targeted therapies available on clinical trials that otherwise would not have been known.
Conclusion:
Plasma-based NGS testing identified actionable genomic alternations in 23 of 56 (41%) patients tested. In most cases, this information was supplementary to that obtained from tumor-based NGS and partially concordant in matched cases. These findings support continued efforts to establish the value of cfDNA in those cases where repeat tissue biopsy is contraindicated or may pose undesirable risk of complications, or when tissue-biopsy based NGS is inadequate or uninformative.
