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Nalini Gupta



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    P1.09 - Pathology (Not CME Accredited Session) (ID 941)

    • Event: WCLC 2018
    • Type: Poster Viewing in the Exhibit Hall
    • Track:
    • Presentations: 2
    • Moderators:
    • Coordinates: 9/24/2018, 16:45 - 18:00, Exhibit Hall
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      P1.09-15 - Preliminary Experience with Liquid Biopsies in a Resource Constrained Setting and its Impact on Treatment Decision Making (ID 13411)

      16:45 - 18:00  |  Author(s): Nalini Gupta

      • Abstract
      • Slides

      Background

      Liquid biopsies are potentially useful for molecular testing in the presence of inadequate tissue and for detection of resistance mechanisms in EGFR mutated NSCLC patients. Initial experience with liquid biopsies for advanced/metastatic NSCLC patients in a resource constrained setting is described herein.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      Retrospective audit of liquid biopsies performed over a 21-month period for NSCLC patients at a tertiary referral centre in North India. Testing methods included digital-droplet-PCR (ddPCR), Next-Generation-Sequencing (NGS) and Real-Time-PCR (RT-PCR). ddPCR was used to detect specific EGFR mutations (L858R exon21, E746_A750 exon19 deletions and T790M exon20) in ctDNA (detection limit based upon amplifiable DNA ranging from 0.5%-<0.01% of mutant allele). For NGS, cfDNA extracted from plasma was subjected to target enrichment by high multiplex PCR amplification and analyzed for mutations using gene panel (BRAF, EGFR, ERBB2/HER2, KRAS, MET) on the Ion Proton semiconductor sequencer (Life Technology, USA). RT-PCR assay using EGFR-RT52 kit (EntroGen USA) detects known somatic mutations in exons 18-21 of EGFR by amplifying mutant-specific sequences and relies on fluorescent probes for detection (detection limit of 1%).

      4c3880bb027f159e801041b1021e88e8 Result

      42 patients [61.9% (n=26) males] underwent liquid biopsies. ddPCR, NGS and RT-PCR were performed in 31(73.8%), 7(16.7%) and 4(9.5%) patients respectively. Timing was prior to/during first-line treatment in 23(54.8%) and at progression on first-line treatment in 19(45.2%) patients. In the former, indication was inadequate tissue for molecular analysis (n=15), detection of other targetable mutation (after EGFR wild type status on tissue; n=3) and checking ctDNA status of T790M exon 20 detected in tissue (n=5). Among 19 patients with progression on first-line treatment, 17 were those with a sensitizing EGFR mutation at baseline who had progressed on EGFR-TKI of which 47.1% (n=8) were found to have T790M exon 20 mutation. The primary EGFR sensitizing mutation detected in tissue at baseline was also detected in ctDNA in 9 of 20 patients with a sensitivity of 45.0%. Agreement between results of tissue testing and liquid biopsy testing for EGFR mutations was 48.0% (12/25). Potential change in management with use of liquid biopsies was observed in 12 patients (28.6% overall and 52.6% if done at progression).

      8eea62084ca7e541d918e823422bd82e Conclusion

      Preliminary experience in our resource constrained setting indicates that greatest utility of liquid biopsies is for EGFR mutated patients with progression on EGFR-TKI wherein T790M detection rates are comparable to those reported in literature. However, the overall sensitivity and agreement is lower than that reported in literature and perhaps may be related to small number of patients.

      6f8b794f3246b0c1e1780bb4d4d5dc53

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      P1.09-31 - Preliminary Experience with Liquid Biopsies in a Resource Constrained Setting and Its Impact on Treatment Decision Making (ID 11718)

      16:45 - 18:00  |  Author(s): Nalini Gupta

      • Abstract

      Background

      Liquid biopsies are potentially useful for molecular testing in the presence of inadequate tissue and for detection of resistance mechanisms in EGFR mutated NSCLC patients. Initial experience with liquid biopsies for advanced/metastatic NSCLC patients in a resource constrained setting is described herein.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      Retrospective audit of liquid biopsies performed over a 21-month period for NSCLC patients at a tertiary referral centre in North India. Testing methods included digital-droplet-PCR (ddPCR), Next-Generation-Sequencing (NGS) and Real-Time-PCR (RT-PCR). ddPCR was used to detect specific EGFR mutations (L858R exon21, E746_A750 exon19 deletions and T790M exon20) in ctDNA (detection limit based upon amplifiable DNA ranging from 0.5%-<0.01% of mutant allele). For NGS, cfDNA extracted from plasma was subjected to target enrichment by high multiplex PCR amplification and analyzed for mutations using gene panel (BRAF, EGFR, ERBB2/HER2, KRAS, MET) on the Ion Proton semiconductor sequencer (Life Technology, USA). RT-PCR assay using EGFR-RT52 kit (EntroGen USA) detects known somatic mutations in exons 18-21 of EGFR by amplifying mutant-specific sequences and relies on fluorescent probes for detection (detection limit of 1%).

      4c3880bb027f159e801041b1021e88e8 Result

      42 patients [61.9% (n=26) males] underwent liquid biopsies. ddPCR, NGS and RT-PCR were performed in 31(73.8%), 7(16.7%) and 4(9.5%) patients respectively. Timing was prior to/during first-line treatment in 23(54.8%) and at progression on first-line treatment in 19(45.2%) patients. In the former, indication was inadequate tissue for molecular analysis (n=15), detection of other targetable mutation (after EGFR wild type status on tissue; n=3) and checking ctDNA status of T790M exon 20 detected in tissue (n=5). Among 19 patients with progression on first-line treatment, 17 were those with a sensitizing EGFR mutation at baseline who had progressed on EGFR-TKI of which 47.1% (n=8) were found to have T790M exon 20 mutation. The primary EGFR sensitizing mutation detected in tissue at baseline was also detected in ctDNA in 9 of 20 patients with a sensitivity of 45.0%. Agreement between results of tissue testing and liquid biopsy testing for EGFR mutations was 48.0% (12/25). Potential change in management with use of liquid biopsies was observed in 12 patients (28.6% overall and 52.6% if done at progression).

      8eea62084ca7e541d918e823422bd82e Conclusion

      Preliminary experience in our resource constrained setting indicates that greatest utility of liquid biopsies is for EGFR mutated patients with progression on EGFR-TKI wherein T790M detection rates are comparable to those reported in literature. However, the overall sensitivity and agreement is lower than that reported in literature and perhaps may be related to small number of patients.

      6f8b794f3246b0c1e1780bb4d4d5dc53