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Specialist Advice — 6 minutes

What are liquid biopsies?

Dr Nicolas Tétreault, PhD, CSPQ, FCACB
Dr Nicolas Tétreault, PhD, CSPQ, FCACB
Clinical Biochemist - Scientific Director

The future of breast cancer screening could be a simple blood test

Genetic science is evolving rapidly. It took 15 years and more than a billion dollars to sequence the first human genome in 2001, but in 2019 we can accomplish the same work in less than 24 hours, for less than $1,000. These advances have fostered a revolution in medicine, allowing us to routinely achieve precise diagnostics and personalized treatments that make a real difference for patients every day. Nowhere is that more obvious than in the advancing science of cancer treatment.

Beyond invasive cancer screening with genomics

One of the specialties that has benefited most from advances in genomics is oncology — the study of tumours. With modern DNA-sequencing technologies, we can read a tumour cell’s DNA and access precious information to help us better treat any underlying cancer, without always needing to resort to traditional, invasive biopsy procedures. In the past, getting the fine medical details on a tumour cell required surgical techniques in order to remove a redundant piece of the affected tissue, which could often be hard to reach or completely inaccessible. With a liquid biopsy, we can determine the odds of a good response to treatment and the chances of recurrence simply from information encoded in the bloodstream.

It has long been known that DNA is released from cells around the body to circulate freely in the blood system. By the mid-1970s, it was understood that cancer patients have a blood-DNA concentration higher than non-cancer patients, and also that this concentration was dropping as treatment took effect [1]. These discoveries led to what we now call liquid biopsies.

You can picture a liquid biopsy as a basic blood draw, but instead of looking at proteins or cells that are normally present in the blood, we take the sample and look for the DNA signature of a cancer. While this technique is not yet in routine use in clinics, there are some types of cancer where its use is already proving very valuable. The best example is for patients with non-small cell lung cancer, where obtaining tissue biopsies is very invasive and risky. Some of these patients may benefit from a liquid biopsy (non-invasive) instead of a tissue biopsy (invasive) in order to obtain critical information about their cancer and better guide the treatment [2].

Liquid biopsies in breast cancer screening

What about breast cancer? Will this type of test change the way we screen and treat it? It’s too early to say for sure, but considerable efforts are ongoing to answer the question, with many heavily funded companies going after this dream.

One important endeavour is the clinical trial STRIVE started by Grail [3], a Silicon Valley-based healthcare company. This trial has enrolled about 100,000 women and aims at early detection of breast cancer (amongst other cancers) through liquid biopsies, with the intent of developing a simple blood test to detect cancer before symptoms appear, and even before imaging exams can detect the tumour.

We are not there yet, though, and we might not even get there in the end. Even if this all seems very promising, many experts warn us not to get our hopes up [4]. There are great challenges ahead. Many think early detection might not be accurate enough to be routinely applied in routine testing, and there is also the important and counterintuitive point that some tumours might actually be better off left alone and undetected — some breast tumours, for example, can take more than 19 years to develop into a symptomatic cancer and then become a real threat for the woman [5]. Treating an indolent breast cancer with chemotherapy and radiotherapy may ultimately make a patient sicker than leaving it in place.

Nevertheless, it’s probable that liquid biopsies will become a very useful tool in many aspects of breast cancer treatment, such as characterization of cancer type to better guide treatment, monitoring of recurrence, and of treatment efficiency. All of that, with just a simple blood draw.

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  1. Leon, S A, A Green, M J Yaros, and B Shapiro. “Radioimmunoassay for Nanogram Quantities of DNA.” Journal of immunological methods. U.S. National Library of Medicine, December 1975.
  2. “Roche Launches the Cobas® EGFR Mutation Test v2 for Use with Either Plasma or Tumor Tissue Samples.” Roche. Accessed September, 2019.
  3. “The STRIVE Study: Development of a Blood Test for Early Detection of Multiple Cancer Types.” U.S. National Library of Medicine. Accessed September 2019.
  4. “Bardia Weighs in on the Evolving Role of Liquid Biopsies in Breast Cancer.” Targeted Oncology. Accessed September 2019.
  5. Heitzer, Ellen, Samantha Perakis, Jochen B. Geigl, and Michael R. Speicher. “The Potential of Liquid Biopsies for the Early Detection of Cancer.” Npj Precision Oncology 1, no. 1 (2017).