Our blood carries a wealth of information about what’s happening inside the body.

For people with cancer, this can include valuable clues about their tumour. For example, genetic changes in tumour DNA that circulates in the bloodstream, known as circulating tumour DNA (ctDNA), can help clinicians match patients to the most effective treatments for their cancer.

Testing blood or other bodily fluids in this way is known as a liquid biopsy and can help avoid the need for a biopsy of the tumour itself.

Liquid biopsy tests are already available in routine care for some patients with lung and breast cancer (in England and Wales), helping to identify the most appropriate treatments for patients and give them the best chance of a good outcome. In the case of lung cancer, liquid biopsy testing can also help with reducing the time to treatment. Recently, liquid biopsy testing was approved (in England) for patients with a cancer where it’s unclear where the cancer first started, also known as cancer of unknown primary (CUP).

Whilst only a small number of liquid biopsy tests have reached routine care so far, research in this space is moving quickly. In this article, we’ll explore where the evidence is emerging and how health systems can prepare for adoption so the benefits of these tests can be realised sooner.

Some liquid biopsy tests are being evaluated for use in the NHS

Within this active research space are initiatives such as the Circulating Tumour Biomarker Network of Excellence in England and the QuicDNA Max programme in Wales, which are exploring how liquid biopsy testing could be used in health systems in the UK.

Helping more patients access new therapies

For patients who’ve run out of standard treatment options, clinical trials can provide opportunities to access new treatments. But finding the right trial for each person can be challenging, as researchers need to match the genetic make-up of someone’s cancer to the treatment most likely to work for them. This usually relies on genomic testing using tissue samples, but this doesn’t always work well. Good-quality tissue samples can be hard to get, and they may not provide the most accurate and up-to-date information about someone’s tumour. For example, a sample may have been taken at an early stage of a patient’s care, and their cancer may have changed in response to previous treatments. Being able to test ctDNA in someone’s blood could therefore provide a more accessible and real-time snapshot of their tumour and make it faster and easier for doctors to match them to the best trial.

Making it easier to diagnose cancers affecting the liver, pancreas and biliary system

For people with liver, pancreas and biliary system cancers, it’s difficult for doctors to get enough information to diagnose the disease and guide their treatment.   These tumours can be difficult to reach, requiring invasive diagnostic procedures that may not produce clear results and may need to be repeated. ctDNA testing could offer a quicker and less invasive way to obtain information about a patient’s tumour and help clinicians make treatment decisions sooner, when it’s more likely to work.

Simplifying follow-up for patients with germ cell tumours

Patients with germ cell tumours (cancers that start in reproductive cells) may need years of follow-up after treatment, often involving regular CT or MRI scans to check whether their cancer has returned. While effective, this monitoring can be time-consuming, cause anxiety, and expose some patients to cumulative radiation. It can also be expensive for health systems. A different type of liquid biopsy, one that analyses circulating microRNA (miRNA), could replace regular imaging and offer a less invasive way to monitor patients. This approach could help make follow-up less burdensome for patients while reducing costs for health systems.

The evidence is growing in other areas

Some applications of liquid biopsy testing are further away from use in routine care but look promising.

Can liquid biopsy testing help clinicians spot treatment resistance or relapse earlier?

Researchers are exploring whether repeat or ‘serial’ ctDNA testing during treatment could help identify genetic changes that make a cancer resistant to treatment. It could also help detect signs of cancer returning, before a patient experiences symptoms or the tumour can be seen on imaging. In both cases this could create opportunities to adjust treatment plans earlier, but more evidence is needed to determine whether acting on these earlier signals actually leads to better outcomes for patients. This is an active area of research, particularly in breast cancer, with studies such as SERENA-6 and TRAK-ER.

Can using liquid biopsies to make treatment decisions actually improve outcomes?

Many people with cancer will need more than one type of treatment, for example having chemotherapy or immunotherapy after surgery, known as adjuvant therapy. However, current tests aren’t precise enough to tell which patients will need this type of treatment and which don’t. By looking for tiny traces of cancer remaining after primary treatment, known as minimal residual disease or MRD, some patients may be able to safely avoid unnecessary treatment. And it may help determine when people need more or different treatment to reduce the risk of their cancer coming back. Research has shown that detecting ctDNA in the blood after surgery is linked to cancer coming back and now studies, including in colorectal and bladder cancer, are investigating whether changing a patient’s treatment based on this can improve their outcomes.

What needs to happen before more patients can benefit?

Before a liquid biopsy test can be introduced into routine care, researchers and health systems need to understand whether it improves patient outcomes, is cost-effective, and can be delivered reliably in practice.

Realising the potential of liquid biopsy tests will depend not only on scientific advances, but also on ensuring health systems are ready to translate innovation into benefits for patients. We need to:

• Understand the research pipeline to support planning and efficient adoption
• Identify where changes to cancer care pathways are needed so the benefits of liquid biopsy testing can be realised, such as stopping testing of tissue samples where appropriate
• Make use of specialist expertise on genomic tumour advisory boards so that test results can be interpreted accurately
• Review real world data to monitor implementation and spot opportunities for improvement

At Cancer Research UK, we’re monitoring developments in the field to understand how liquid biopsy tests may help improve patient outcomes in the years ahead. As new evidence emerges, we’ll work with researchers, health systems and policymakers to ensure these benefits reach the right patients quickly and equitably. If you have any questions on this article or topic area, get in touch with our Strategic Evidence team at [email protected].