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D.H. Hwang



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    MA 20 - Recent Advances in Pulmonology/Endoscopy (ID 685)

    • Event: WCLC 2017
    • Type: Mini Oral
    • Track: Pulmonology/Endoscopy
    • Presentations: 1
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      MA 20.14 - Genotyping of Lung Cancer Using Cell-Free DNA (cfDNA) from Cytologic Supernatant (CSN) (ID 9057)

      15:55 - 16:00  |  Author(s): D.H. Hwang

      • Abstract
      • Presentation
      • Slides

      Background:
      Tumor genotyping is transforming lung cancer care but increasingly requires more tumor tissue. Advances in minimally invasive bronchoscopic techniques increase access to small lesions, but often result in smaller samples. With the advent of new cfDNA (“liquid biopsy”) genotyping technologies, we hypothesized that CSN might increase the yield from small FNAs, facilitating cancer genotyping.

      Method:
      We studied patients with known or suspected lung cancer undergoing FNAs. CSN, which is usually discarded, was collected under IRB approval. cfDNA was extracted after a hard spin (1600 Gs) and tested by both ddPCR (EGFR, KRAS mutations) and targeted next-generation sequencing (NGS).

      Result:
      14 patients with suspected or known lung cancer were studied at time of analysis (final diagnosis: 2 non-malignant, 9 adenocarcinomas, 1 small-cell carcinoma, 2 squamous cell carcinomas), including 12 EBUS-TBNAs and 2 CT-guided FNAs. Among 6 known KRAS and EGFR mutations, all could be detected with ddPCR of CSN, with allelic fraction (AF) ranging from 1%-46% (median 8.5%). No ddPCR false positives were seen across 9 cases. NGS analysis was piloted on 7 specimens; 5 failed due to insufficient residual DNA. In one specimen, an EGFR exon 19 deletion was detected at 6% AF (2% AF ddPCR). In the other, a BRAF V600E, PIK3CA E784D and TP53 V274F mutations were detected at 48% (46% AF ddPCR), 18% and 86% AF, respectively.

      Conclusion:
      Cytology supernatant, usually discarded, may be a rich source of fresh tumor DNA, increasing the yield from FNAs. This widely available biospecimen has potential for aiding resistance genotyping, reducing turnaround time of cancer genotyping, and possibly a future role in clarifying the malignant potential of non-diagnostic biopsies. Enrollment continues in order to optimize this biospecimen for NGS. Figure 1



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