Liquid Biopsy

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Application

In liquid biopsies, the presence of altered ctDNA is an indicator of the genetic composition of a tumour, and the quantity of ctDNA can reflect prognosis and predict response to treatment (including cytogenetic variations, copy number variations, mutations and changes due to methylation). The ESMO Precision Medicine Working Group includes ctDNA testing for NTRK1/2/3 gene fusions in several tumour types when there is no tissue available [1]. In cases where detection is suboptimal and tissue is available, the Group recommends repeating the test using tissue.

The ability to detect ctDNA depends on its free circulating fraction. When there is a low ctDNA fraction available, the most appropriate techniques for the detection of the genetic alterations are digital polymerase chain reaction (dPCR), beaming, safe-sequencing system (Safe-SeqS), cancer personalized profiling by deep sequencing (CAPP-Seq) and tagged-amplicon deep sequencing (TAm-Seq), whereas when the ctDNA fraction is high, the most useful techniques are whole genome sequencing (WGS), exome and plasma-sequencing, personalized analysis of rearranged ends (PARE), and whole methylome analysis [2].

References

1. Pascual J, Attard G, Bidard FC et al. ESMO recommendations on the use of circulating tumour DNA assays for patients with cancer: a report from the ESMO Precision Medicine Working Group. Ann Oncol. 2022 Jun 9:S0923-7534(22)01721-5.

2. Rolfo C, Cardona AF, Cristofanilli M et al. Challenges and opportunities of cfDNA analysis implementation in clinical practice: Perspective of the International Society of Liquid Biopsy (ISLB). Crit Rev Oncol Hematol. 2020 Jul;151:102978.Liquid biopsies come of age: towards implementation of circulating tumour DNA. Nat Rev Cancer 2017; 17: 223-238.