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Y. Gong
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MA 01 - SCLC: Research Perspectives (ID 650)
- Event: WCLC 2017
- Type: Mini Oral
- Track: SCLC/Neuroendocrine Tumors
- Presentations: 1
- Moderators:John V Heymach, Eun Kyung Cho
- Coordinates: 10/16/2017, 11:00 - 12:30, Room 503
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MA 01.03 - The Potential of ctDNA Sequencing in Disease Monitoring and Depicting Genomic Evolution of Small-Cell Lung Cancer Under Therapy (ID 9682)
11:00 - 12:30 | Author(s): Y. Gong
- Abstract
- Presentation
Background:
Although small cell lung cancer (SCLC) is sensitive to initial therapy, almost all patients relapse and survival remains poor. Outgrowth of treatment-resistant subclones could be responsible for recurrence. However, genomic evolution of SCLC after treatment hasn’t been well investigated, partially due to the challenge of obtaining longitudinal samples. CT is the standard modality for response assessment and disease monitoring. But it doesn’t always accurately assess the disease status. SCLC is characterized by early hemagenous spread, which makes circulating tumor DNA (ctDNA) analysis a promising modality for genomic profiling and disease monitoring of SCLC.
Method:
Targeted-capture deep sequencing (mean target coverage 538x-1866x) of 545 cancer genes was performed to 44 ctDNA samples collected before therapy as baseline and at different timepoints during treatment from 23 SCLC patients. Pretreatment tumor biopsies from 8 patients were also sequenced (mean target coverage 348x-1281x) of the same gene panel. DNA from peripheral blood mononuclear cells was served as the germline control.
Result:
Mutations were identified in all 44 ctDNA samples with a median of 16 mutations per sample (average mutation burden of 6.6/Mb). TP53 and RB1 were the most frequently mutated genes, detected in 91% (21/23) and 65% (15/23) patients, respectively. 74 mutations were identified from the 8 tumor biopsies, among which, 69 (93.2%) were detected in matched ctDNA. We inferred subclonal architecture of each ctDNA sample based on cancer cell fraction derived using PyClone. A median of 10 (ranging 2-26) subclones was inferred from each ctDNA sample and only 17% (2% to 60.%) of mutations were clonal mutations suggesting substantial genomic heterogeneity. Single gene mutations were not associated with survival. However, mean variant allele frequency of clonal mutations (clonal-VAF) at baseline was associated with progression-free survival (PFS) and overall survival (OS) independent of stage, age, or platinum sensitivity. The median PFS of patients with higher versus lower than median clonal-VAF was 5.2 months (95% CI, 4.6 to 5.8 months) versus 10.0 months (95% CI, 9.3 to 10.7 months), p=0.002. The median OS was 8.1 months (95% CI, 5.5 to 10.7 months) versus 24.9 months (95% CI, 0.0 to 51.2 months) in patients with higher versus lower than median clonal-VAF, respectively, p=0.004. Analysis of serial ctDNA before and during treatment showed that clonal-VAF closely tracked closely with treatment responses.
Conclusion:
ctDNA sequencing is a promising modality for genomic profiling and disease monitoring for SCLC patients. Clonal VAF may be a better ctDNA metric than single gene mutations.
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P3.16 - Surgery (ID 732)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Surgery
- Presentations: 1
- Moderators:
- Coordinates: 10/18/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P3.16-053 - Genomic Challenges for Lung Cancers with Multiple Pulmonary Sites of Involvement (ID 9918)
09:30 - 16:00 | Author(s): Y. Gong
- Abstract
Background:
Patients with lung cancer who harbor multiple pulmonary sites of disease have been challenging to classify. Although the International Association for the Study of Lung Cancer Staging and Prognostic Factors Committee propose to tailor TNM classification of multiple pulmonary sites of lung cancer to reflect the unique aspects of four different patterns of presentation, tough challenges faced by clinicians are still not easily overcome.
Method:
Surgical tumor and normal tissue specimens were collected from six patients who were diagnosed with pathologically confirmed multiple lung cancers, with each tumor in the separate lobe, and treated at Beijing Cancer Hospital, Peking University, Beijing, China. Whole-exome sequencing was used to depict the genomic profiles of each tumor, and the average sequencing depth was 123× per sample (range, 84× to 154×; s.d., 19×).
Result:
In this study, we analyzed genomic profiles of 12 tumors from 6 patients with multiple lung cancers. Eight tumors from 4 patients demonstrated distinct genomic profiles, suggesting all were independent primary tumors, which were consistent with comprehensive histopathological assessment. Noteworthy common genomic characteristics were seen in 4 tumors from 2 patients. Compared with TCGA lung cancer cohort, one out of 6 patients carried significantly higher somatic nonsynonymous mutational burden, which were also discrepant between two separate lesions. Figure 1
Conclusion:
The current findings suggest that the tailor TNM classification of multiple pulmonary sites of lung cancer still encounter real-world challenges. A deeper understanding of the spatial and temporal dynamics of the carcinogenesis and evolution of lung cancer will be required to address these challenges.
