Blood test could help detect cancer in people with nonspecific symptoms

Source: The Guardian

Scientists have developed a blood test that could help detect cancer in people with nonspecific symptoms such as unexplained weight loss or fatigue.

If validated, the test could enable cancer patients to be identified earlier, when they are more likely to respond to treatment, and help flag up who could benefit from early access to drugs designed to tackle metastatic cancer. The test can also tell if the disease has spread.

There is currently no clear route through which someone with nonspecific symptoms that could be cancer is referred for further investigation. NHS rapid diagnostic centres are being set up to support faster and earlier cancer diagnosis, but often patients will be examined by their GP, and if they can’t identify an obvious cause of their symptoms then the patient will simply be told to come back if they get worse.

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“The problem we’ve had in the past is that if they do have cancer, that cancer is growing all the time, and when they come back the cancers are often quite advanced,” said Dr James Larkin, of the University of Oxford, who was involved in the research.

Although it is difficult to know precisely how many individuals fall into this category, “it is likely to be tens of thousands of patients across the UK,” Larkin said. “We’re hoping to capture these patients when they come to the GP, to give them an immediate referral option.

“The moment you can say ‘you have cancer’, it provides a strong incentive to send that patient for an imaging investigation to see if you can find that cancer.”

The new test utilises a technology called nuclear magnetic resonance (NMR) spectroscopy, which profiles levels of small molecules called metabolites in the blood. Healthy individuals have different metabolic “fingerprints” to those with localised or metastatic cancer.

In a study published in the journal Clinical Cancer Research, Larkin and colleagues analysed samples from 300 patients with nonspecific but concerning symptoms of cancer, such as fatigue and weight loss, and found that the test correctly detected cancer in 19 out of every 20 of those with the disease. It cannot yet pinpoint the type of tumour they have, but this is the ultimate goal.

The test could also distinguish between patients with localised or metastatic cancer with 94% accuracy, making this the first blood test to be able to detect if a person’s cancer has spread without knowing the type of tumour they have.

“Such information changes how you treat patients,” Larkin said. For instance, certain immunotherapies have been shown to increase survival rates among people with metastatic cancer, but they are expensive and have side effects. “We don’t want to prescribe them to everyone, but there are patients out there that would absolutely benefit if you could only identify them early enough.

A different type of blood test that aims to detect circulating tumour DNA (ctDNA) is being trialled in the NHS, but metabolic changes may be detectable earlier, while ctDNA technology also requires you to know which mutations to look for when finding a tumour.

The next step is to confirm the accuracy of the test in 2,000 to 3,000 British patients with nonspecific symptoms, which Larkin hopes could happen within the next two years. This data would then be submitted to national regulatory agencies responsible for authorising such tests.