Abstract
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. 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%). 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). 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.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.