Liquid Biopsy via PCR: Non-Invasive Monitoring of Cancers and Other Genetic Disorders

Abstract: Tissue biopsies are the standard for diagnosing and monitoring cancer, but they are invasive and impractical for repeated sampling. Liquid biopsy, analyzing biological fluids like blood for tumor-derived materials, offers an alternative. This article explores how PCR techniques are used in liquid biopsy for non-invasive monitoring of cancers and other genetic disorders.


Accurate diagnosis and disease monitoring are essential for effective patient management. Tissue biopsies, where a tissue sample is surgically removed and analyzed, are the main method for cancer diagnosis. However, these procedures are invasive, carry risks of complications, and are not suitable for repeated monitoring .

Liquid biopsy offers a new approach for diagnosing and monitoring cancer by analyzing readily available biological fluids, mainly blood. This approach involves detecting and characterizing tumor-derived materials present in circulation, including:

  • Circulating tumor cells (CTCs)
  • Cell-free DNA (cfDNA), including circulating tumor DNA (ctDNA)
  • Exosomes

Comparison of traditional tissue biopsy and liquid biopsy. The schematic illustrates the advantages that liquid biopsies have gained over traditional invasive surgical methods over the past decade. Shown here are methods of extracting a test sample which usually includes a small tissue fragment in case of tissue biopsies and blood in LBs. Analytes that are isolated and monitored in LBs include ctDNA, CTCs, and tumor EVs

PCR: A Key Tool for Liquid Biopsy Analysis

Polymerase chain reaction (PCR) is a fundamental technique in molecular biology and plays a vital role in analyzing liquid biopsies. PCR amplifies specific DNA sequences, allowing detection and quantification of tumor-derived genetic alterations in cfDNA isolated from blood samples.

everal PCR-based techniques are used in liquid biopsy:

  • Digital PCR (dPCR): Offers superior sensitivity for detecting rare mutant alleles in ctDNA compared to traditional PCR. 
  • Droplet Digital PCR (ddPCR): A variation of dPCR that partitions the sample into thousands of droplets, further enhancing sensitivity for ctDNA detection.
  • Multiplex PCR: Enables the simultaneous detection of mutations in multiple genes associated with cancer or other genetic disorders within a single reaction, improving efficiency.

Consider utilizing commercially available PCR kits specifically designed for high sensitivity applications, such as those offered by Gentaur

Applications of Liquid Biopsy via PCR:

The use of PCR in liquid biopsy holds promise for various applications:

  • Early Cancer Detection: Detecting tumor-derived mutations in ctDNA could potentially facilitate early cancer diagnosis before symptoms appear.
  • Monitoring Treatment Response: Serial analysis of ctDNA using PCR can be used to monitor a patient's response to cancer treatment and detect potential relapse early.
  • Personalized Medicine: Identifying specific mutations in ctDNA through PCR can aid in selecting targeted therapies and tailoring treatment strategies for individual patients.
  • Monitoring Other Genetic Disorders: PCR-based analysis of cell-free DNA in liquid biopsy can be used to monitor other genetic disorders with known genetic signatures.

Clinical application of urine‐based liquid biopsy in bladder cancer. ddPCR, droplet digital polymerase chain reaction; ELISA, enzyme‐linked immunosorbent assay; MS, mass spectrometry; NGS, next‐generation sequencing; RT‐PCR, quantitative real‐time polymerase chain reaction; WB, Western blot. Figure is created with


Liquid biopsy via PCR offers a promising approach for non-invasive monitoring of cancers and other genetic disorders. Utilizing PCR techniques for ctDNA analysis in readily obtainable biological fluids has the potential to revolutionize cancer diagnosis, treatment monitoring, and personalized medicine strategies. As research progresses, overcoming current limitations and further refining liquid biopsy techniques will pave the way for its wider clinical application.