Liquid biopsy, a paradigm shift in oncology: what interventional radiologists should know.

The acquisition of adequate tumor sample is required to verify primary tumor type and specific biomarkers and to assess response to therapy. Historically, invasive surgical procedures were the standard methods to acquire tumor samples until advancements in imaging and minimally invasive equipment facilitated the paradigm shift image-guided biopsy. Image-guided biopsy has improved sampling yield and minimized risk to the patient; however, there are still limitations, such as its invasive nature and its consequent limitations to longitudinal tumor monitoring. The next paradigm shift in sampling technique will need to address these issues to provide a more reliable and less invasive technique. Recently, liquid biopsy (LB) has emerged as a non-invasive alternative to tissue sampling. This technique relies on direct sampling of blood or other bodily fluids in contact with the tumor in order to collect circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and circulating RNAs-in particular microRNA (miRNAs). Clinical applications of LB involve different steps of cancer patient management including screening, detection of disease recurrence, and evaluation of acquired resistance. With any paradigm shift, old techniques are often relegated to a secondary option. Although image-guided biopsies may appear as a passive spectator on the rapid advancement of LB, the two techniques may well be codependent. Interventional radiology may be integral to directly sample the liquid surrounding or draining from the tumor. In addition, LB may help to correctly select the patients for image-guided loco-regional treatments, to determine its treatment endpoint, and to early detect recurrence. KEY POINTS: • Liquid biopsy is a novel technology with potential high impact in the management of patients undergoing image-guided procedures. • Interventional radiology procedures may increase liquid biopsy sensitivity through direct fluid sampling. • Liquid biopsy techniques may provide a venue for improving patients' selection and enhance outcomes of interventional loco-regional therapies performed by interventional radiologists.