In just a few years, liquid biopsy has been adopted as an efficient assay for cancer testing. The test is simple to conduct and has a quick turnaround time, and can work for both solid and hematological tumors. Additionally, liquid biopsies work across multiple specimen types, and can be used to identify the molecular profiles, tumor evolutions and resistance mechanisms of patients.
In 2016, the FDA approved the first liquid biopsy test for epidermal growth factor receptors, or EGF. With new and enhanced technologies continuing to be developed, demand is forecast to keep on a steady rise.
Digital PCR (dPCR) is a complementary technology to liquid biopsy, especially for assessing circulating tumor DNA (ctDNA) due to its high sensitivity. dPCR is also cost effective and does not require the need of specialized bioinformatics like NGS. It also offers superior precision compared to PCR, as the test consists of up to millions of independent PCR reactions in separate microdroplet-based compartments. In dividing the sample into so many droplets, there is a low chance that more than one DNA molecule will be amplified in an individual droplet, making the assay exact, extremely reproducible and quantitative.
Cell-free DNA testing is also key, as it is used as a screening test when it is suspected that a patient has secondary resistance to EGFR tyrosine kinase inhibitors. When a test result is negative, a biopsy is scheduled for the patient. As it can be difficult to assess the level of cell-free DNA in a liquid biopsy sample unless the result is positive, this can lead to false-negative results of liquid biopsies. To address this, many institutions are currently or planning to develop their own cell-free DNA assays, indicating that the growth of liquid biopsy tests will not be slowing down soon.
Source: CAP Today