Circulating cell free deoxyribonucleic acid for tracking early treatment response and disease progression in advanced cancers

Cell free DNA (cfDNA) detected in the blood of cancer patients has important potential applications in cancer diagnosis, prognosis and precision medicine. A small proportion of cfDNA originating from tumour cells, known as cell free tumour DNA (ctDNA), has been shown to closely match the genomic profiles of tumour cells. ctDNA has demonstrated preliminary but promising results as an early on-treatment predictor of treatment response and as a means of tracking disease progression/treatment resistance in advanced cancers. However, the current studies are relatively small and use variable methods for detecting ctDNA and evaluating the performance of the approach. The ctDNA approach needs further developmental work in terms of standardization of ctDNA quantitative methods and techniques and harmonization of methods for evaluating predictive performance and results reporting. Replication of findings in large independent studies with pre-specified analysis plans are a priority direction for future research.