Liquid biopsy in ovarian cancer using circulating tumor DNA and cells: Ready for prime time?

Liquid biopsies hold the potential to inform cancer patient prognosis and to guide treatment decisions at the time when direct tumor biopsy may be impractical due to its invasive nature, inaccessibility and associated complications. Specifically, circulating tumor DNA (ctDNA) and circulating tumor cells (CTCs) have shown promising results as companion diagnostic biomarkers for screening, prognostication and/or patient surveillance in many cancer types. In ovarian cancer (OC), CTC and ctDNA analysis allow comprehensive molecular profiling of the primary, metastatic and recurrent tumors. These biomarkers also correlate with overall tumor burden and thus, they provide minimally-invasive means for patient monitoring during clinical course to ascertain therapy response and timely treatment modification in the context of disease relapse. Here, we review recent reports of the potential clinical value of CTC and ctDNA in OC, expatiating on their use in diagnosis and prognosis. We critically appraise the current evidence, and discuss the issues that still need to be addressed before liquid biopsies can be implemented in routine clinical practice for OC management. •Standardisation of methodologies is required for thorough evaluation of the clinical utility of CTCs in ovarian cancer.•CTC holds key biological information for understanding the metastatic process.•ctDNA is a promising biomarker for early diagnosis and monitoring of ovarian cancer.•DNA methylation patterns in cell-free DNA have potential for early diagnosis of ovarian cancer.