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L. Li
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MA 11 - Emerging Diagnostic/Biomarkers in NSCLC (ID 668)
- Event: WCLC 2017
- Type: Mini Oral
- Track: Advanced NSCLC
- Presentations: 1
- Moderators:M.I. Abdul Wahid, Martin Reck
- Coordinates: 10/17/2017, 11:00 - 12:30, Room 313 + 314
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MA 11.05 - Targeted DNA- and RNA-Based Next-Generation Sequencing for Identifying MET Exon 14 Alterations in Pulmonary Sarcomatoid Carcinoma (ID 9266)
11:00 - 12:30 | Author(s): L. Li
- Abstract
- Presentation
Background:
Highly diverse somatic splice site alteration at MET exon 14 (METex14) result in exon skipping, which is supposed to be a therapeutic target in NSCLC. Here we report detection of METex14 alterations using targeted DNA- and RNA-based Next-Generation Sequencing (NGS) in pulmonary sarcomatoid carcinoma (PSC) with a high frequency of METex14 skipping.
Method:
Tumor specimens were collected from 77 Chinese PSC patients. DNA and RNA were subject to targeted NGS, allowing the detection of somatic splice site alterations and intragenic METex14 skipping respectively. Then, somatic mutations (mutation allele frequency ≥2%) that lead to METex14 skipping were recognized, and Fisher’s exact test was used to examine the association between METex14 skipping and clinical characteristics or other mutations. Two-sided P-values <0.05 were considered statistically significant. Moreover, RT-PCR and Sanger sequencing was also performed on the METex14-positive specimens.
Result:
We have detected genetic aberrations in 77 FFPE samples. For RNA-based NGS, METex14 skipping was identified in 16 (20.78%) of 77 patient cases. And 15 (93.75%) METex14-positive patients were detected somatic mutations by DNA-based NGS, including 12 (80%) cases with splice donor site mutations, 1 (6.67%) cases with splice acceptor site alterations, 1 (6.67%) case with a novel deletion (chr7: 116411868 - 116411883) at MET intron 13 region and 1 (6.67%) case with a novel deletion (chr7: 116412027 - 116412042) at MET exon14 region. In this study, 6 somatic mutations which induce METex14 skipping were firstly discovered. So far, RT-PCR and Sanger sequencing were performed on 3 specimens, including 1 sample with conflicting RNA- and DNA-based NGS results and 2 samples with unreported somatic deletions. According to the results of RT-PCR and Sanger, the unmatched sample was false negative on the basis of DNA-based NGS result. Interestingly, METex14 skipping was mutually exclusive with other recognized genomic alterations (such as mutations in KRAS, BRAF, EGFR, NRAS and PIK3CA), while no significant difference was found between METex14 skipping and single driver gene.
Conclusion:
Mutational events of MET leading to exon 14 skipping are frequent occurred in Chinese PSC patients. DNA-based NGS could discover new somatic mutations which results in METex14 skipping. However, RNA-based NGS could provide more accurate results than DNA-based NGS. METex14 skipping was mutually exclusive with other drivers, thus strongly highlighting its potential oncogenic role.
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P1.07 - Immunology and Immunotherapy (ID 693)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Immunology and Immunotherapy
- Presentations: 1
- Moderators:
- Coordinates: 10/16/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P1.07-044a - Comparison of Tumor Mutational Burden (TMB) Derived from Whole Exome and Large Panel Sequencing in Lung Cancer (ID 9241)
09:30 - 16:00 | Author(s): L. Li
- Abstract
Abstract not provided
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P3.01 - Advanced NSCLC (ID 621)
- Event: WCLC 2017
- Type: Poster Session with Presenters Present
- Track: Advanced NSCLC
- Presentations: 1
- Moderators:
- Coordinates: 10/18/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)
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P3.01-037 - Understanding Mechanisms of Resistance to Osimertinib by Circulating Tumor DNA Genotyping in Advanced Non-Small-Cell Lung Cancer (ID 9267)
09:30 - 16:00 | Author(s): L. Li
- Abstract
Background:
Epidermal growth factor receptor (EGFR) T790M mutation is the most common mechanism for resistance to first- and second-generation EGFR tyrosine kinase inhibitors (TKI). Osimertinib has been demonstrated to overcome EGFR T790M non-small cell lung cancer (NSCLC). However, most of these patients eventually developed resistance after 10 months. Here we performed a comprehensive next generation sequencing (NGS) using circulating tumor DNA (ctDNA) to study resistance mechanisms in patients with advanced NSCLC who had developed resistance to osimertinib, and to provide potential opportunities for treatment.
Method:
10 advanced NSCLC patients were enrolled in this study after progression from first-generation EGFR-TKI treatment. Patients received osimertinib with 80mg daily, the response rate and progression-free survival (PFS) was assessed during treatment. 10ml peripheral blood was collected from patients after progression from osimertinib, and ctDNA genotyping was performed by next-generation sequence (NGS).
Result:
There were 3 patients received gefitinib and 7 patients received erlotinib before osimertinib therapy. All patients confirmed a partial response (PR) on osimertinib, the median PFS was 13.3 months. The initial gene mutation patterns before osimertinib therapy could be classified into two groups: L858R/Exon 19 Deletion (19Del) +T790M, and L858R/19Del+T790M unknown or wild-type. However, after progression from osimertinib, mutation patterns varied from groups. In the L858R/19Del+T790M group, two of six patients detected with L858R/19Del+T790M+C797S, two patients with L858R (+T790M) +HER2 amplification, and two patients with only 19Del+T790M; In the L858R/19Del+T790M unknown or wild-type group, there was only one patient detected with L858R/19Del+C797S mutation, the other three patients detected with only L858R mutation. For the C797S-mutated patients, it showed that T790M and C797S mutation presented in the same allele (cis) in two patients, while in both trans and cis in one patient. Other EGFR mutations were also detected, such as A750P, L792F, E709K, A1013V, L718V, and EGFR amplification.
Conclusion:
Genotyping of ctDNA in osimertinib resistant patients showed that the resistance might be related to specific gene mutation, e.g., EGFR C797S and HER2 amplification. Our findings provide insight that resistance to osimertinib might be different between T790M-mutated patients and T790M wilt-type patients. Combination therapy of osimertinib with other agents may be candidate to overcome the acquired mutation.
