Liquid biopsies are a relatively new technology in cancer diagnostics, but have shown great potential in their ability to detect cancer early. This has led to a significant improvement in the chances of successful treatment. However, the process has a long way to go before doctors can rely on it.

What Are Liquid Biopsies?

It is a non-invasive method for the early detection of tumour as well as the monitoring of tumour during cancer treatment. It provides data concerning the relapse of a tumour long before any symptoms can be observed. Liquid biopsies analyse bodily fluids (mainly blood) for identifying various biomarkers including proteins, such as:

  • circulating tumour cells (CTCs);
  • circulating tumour DNA (ctDNA);
  • cell-free DNA (cfDNA); and
  • proteins biomarkers, exosomes, mRNA, and miRNA

The liquid biopsy global market is expected to reach $3 billion by 2022 at a compound annual growth rate of 26%, predominantly due to the increasing number of cancer diagnoses and favourable government initiatives.

CTCs, which are the precursor to metastasis, are often used as the biomarker in liquid biopsies. The Food and Drug Administration (FDA) has also approved CTCs to predict the outcome of a cancer case. Veridex’s CellSearch has been cleared for clinical use in breast, colorectal and prostate cancer patients. However, research is focused on using CTCs for various other forms of cancer as well.

Alternatively, ctDNA is a relatively new biomarker which has many advantages over CTCs. Tumours continuously shed DNA into the bloodstream by apoptosis; ctDNA is known for tumour mutation and therefore may provide the required information for a suitable course of treatment. ctDNA is preferable to other biomarkers in terms of clinical correlation, as its half-life is approximately two hours and it therefore provides real-time analysis of tumours.

cfDNA has been known about for some time, but its detection and isolation has become possible only recently, thanks to advancements in sequencing technologies. Since it is in its early stages, cfDNA must overcome many obstacles before it can be commercialised. Most of the patent filings in this domain are focused on isolating ctDNA from the large amount of cfDNA available in plasma, which requires ultrasensitive detection. Patent filings are also focused on detecting suitable markers for the identification of cancer.

Protein specific for cancers, such as carcinoembryonic antigen and carbohydrate antigen 19-9, were among the first analytes to be used as biomarkers for blood tests based cancer detections. Such biomarkers have been approved for assessing tumor burden in patients already diagnosed with cancer, particularly during therapy in patients with advanced cancer.

It is debatable which available biomarker is most suitable for the diagnosis of cancer. However, a liquid biopsy undeniably offers the following advantages over a standard biopsy:

  • Biopsy is a surgical procedure and therefore poses a higher risk to patients in comparison to a blood sample.
  • Under-representation of the heterogeneity of a tumour and poor sample availability means that tissue biopsies are of limited value for the assessment of tumours in the advanced stages of cancer.
  • Tracking tumour-associated genetic aberrations in the blood can be used to assess the presence of residual disease, recurrence, relapse and resistance.

Key players in the liquid biopsy domain include:

  • Roche Diagnostics;
  • Qiagen;
  • Adaptive Biotechnologies;
  • GRAIL;
  • Guardant Health;
  • Illumina;
  • Janssen Diagnostics;
  • Myriad Genetics; and
  • Trovagene

So, is liquid biopsy the new benchmark for cancer diagnostics?

The process is far away from being the stand alone method for cancer detection as the information provided by present liquid biopsies is sometimes incomplete and non-reproducible. For now, liquid biopsy is being used to complement a tissue biopsy and monitor the tumour during treatment.

Before liquid biopsies are adapted as the standard for cancer diagnostics, the following information is required:

  • the standardisation of techniques;
  • an assessment of reproducibility and cost-effectiveness; and
  • an assessment prospective validation in clinical trials.

In future, liquid biopsies may provide diagnostics tests for other diseases, as well as prenatal diagnostics. It will be interesting to see its adaptation in healthcare industry and the potential innovation in liquid biopsy.

-Yogesh Soam

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