Clinical application of liquid biopsy based on circulating tumor DNA in non-small cell lung cancer

Implementation of an ISO 15189 accredited next generation sequencing service for cell-free total nucleic acid (cfTNA) analysis to facilitate driver mutation reporting in blood: the experience of a clinical diagnostic laboratory

AIMS

Next generation sequencing (NGS) on tumour tissue is integral to the delivery of personalised medicine and targeted therapy. NGS on liquid biopsy, a much less invasive technology, is an emerging clinical tool that has rapidly expanded clinical utility. Gene mutations in cell-free total nucleic acids (cfTNA) circulating in the blood are representative of whole tumour biology and can reveal different mutations from different tumour sites, thus addressing tumour heterogeneity challenges.

METHODS

The novel Ion Torrent Genexus NGS system with automated sample preparation, onboard library preparation, templating, sequencing, data analysis and Oncomine Reporter software was used. cfTNA extracted from plasma was verified with the targeted pan-cancer (~50 genes) Oncomine Precision Assay (OPA). Assessment criteria included analytical sensitivity, specificity, limits of detection (LOD), accuracy, repeatability, reproducibility and the establishment of performance metrics.

RESULTS

An ISO 15189 accredited, minimally invasive cfTNA NGS diagnostic service has been implemented. High sensitivity (>83%) and specificity between plasma and tissue were observed. A sequencing LOD of 1.2% was achieved when the depth of coverage was >22 000×. A reduction (>68%) in turnaround time (TAT) of liquid biopsy results was achieved: 5 days TAT for in-house analysis from sample receipt to a final report issued to oncologists as compared with >15 days from reference laboratories.

CONCLUSION

Tumour-derived somatic variants can now be reliably assessed from plasma to provide minimally invasive tumour profiling. Successful implementation of this accredited service resulted in:Appropriate molecular profiling of patients where tumour tissue is unavailable or inaccessible.Rapid TAT of plasma NGS results.

Liquid biopsy in non-small cell lung cancer: a meta-analysis of state-of-the-art and future perspectives

Introduction: To date, tissue biopsy represents the gold standard for characterizing non-small-cell lung cancer (NSCLC), however, the complex architecture of the disease has introduced the need for new investigative approaches, such as liquid biopsy. Indeed, DNA analyzed in liquid biopsy is much more representative of tumour heterogeneity. Materials and methods: We performed a meta-analysis of 17 selected papers, to attest to the diagnostic performance of liquid biopsy in identifying EGFR mutations in NSCLC. Results: In the overall studies, we found a sensitivity of 0.59, specificity of 0.96 and diagnostic odds ratio of 24,69. Since we noticed a high heterogeneity among different papers, we also performed the meta-analysis in separate subsets of papers, divided by 1) stage of disease, 2) experimental design and 3) method of mutation detection. Liquid biopsy has the highest sensitivity/specificity in high-stage tumours, and prospective studies are more reliable than retrospective ones in terms of sensitivity and specificity, both NGS and PCR-based techniques can be used to detect tumour DNA in liquid biopsy. Discussion: Overall, liquid biopsy has the potential to help the management of NSCLC, but at present the non-homogeneous literature data, lack of optimal detection methods, together with relatively high costs make its applicability in routine diagnostics still challenging.