Liquid biopsies: Potential and challenges

Int J Cancer. 2021 Feb 1;148(3):528-545. doi: 10.1002/ijc.33217. Epub 2020 Aug 10.


The analysis of tumor cells or tumor cell products obtained from blood or other body fluids ("liquid biopsy" [LB]) provides a broad range of opportunities in the field of oncology. Clinical application areas include early detection of cancer or tumor recurrence, individual risk assessment and therapy monitoring. LB allows to portray the entire disease as tumor cells or tumor cell products are released from all metastatic or primary tumor sites, providing comprehensive and real-time information on tumor cell evolution, therapeutic targets and mechanisms of resistance to therapy. Here, we focus on the most prominent LB markers, circulating tumor cells (CTCs) and circulating tumor-derived DNA (ctDNA), in the blood of patients with breast, prostate, lung and colorectal cancer, as the four most frequent tumor types in Europe. After a brief introduction of key technologies used to detect CTCs and ctDNA, we discuss recent clinical studies on these biomarkers for early detection and prognostication of cancer as well as prediction and monitoring of cancer therapies. We also point out current methodological and biological limitations that still hamper the implementation of LB into clinical practice.

Keywords: blood; carcinomas; circulating tumor DNA; circulating tumor cells; liquid biopsy.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Biomarkers, Tumor / blood
  • Biomarkers, Tumor / genetics
  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / genetics
  • Breast Neoplasms / pathology
  • Circulating Tumor DNA / blood*
  • Colorectal Neoplasms / genetics
  • Colorectal Neoplasms / pathology
  • Early Detection of Cancer
  • Female
  • Humans
  • Liquid Biopsy
  • Lung Neoplasms / drug therapy
  • Lung Neoplasms / genetics
  • Lung Neoplasms / pathology
  • Male
  • Molecular Targeted Therapy
  • Neoplasms / drug therapy
  • Neoplasms / genetics
  • Neoplasms / pathology*
  • Neoplastic Cells, Circulating / pathology*
  • Prognosis
  • Prostatic Neoplasms / drug therapy
  • Prostatic Neoplasms / genetics
  • Prostatic Neoplasms / pathology


  • Biomarkers, Tumor
  • Circulating Tumor DNA