Author: Nadeem Badshah
A simple blood test that can detect more than 50 types of cancer before any clinical signs or symptoms of the disease emerge in a person is accurate enough to be rolled out as a screening test, according to scientists.
The test, which is also being piloted by NHS England in the autumn, is aimed at people at higher risk of the disease including patients aged 50 or older. It is able to identify many types of the disease that are difficult to diagnose in the early stages such as head and neck, ovarian, pancreatic, oesophageal and some blood cancers.
Scientists said their findings, published in the journal Annals of Oncology, show that the test accurately detects cancer often before any signs or symptoms appear, while having a very low false positive rate.
The test, developed by US-based company Grail, looks for chemical changes in fragments of genetic code – cell-free DNA (cfDNA) – that leak from tumours into the bloodstream.
The Guardian first reported on the test last year and how it had been developed using a machine learning algorithm – a type of artificial intelligence. It works by examining the DNA that is shed by tumours and found circulating in the blood. More specifically, it focuses on chemical changes to this DNA, known as methylation patterns.
Now the latest study has revealed the test has an impressively high level of accuracy. Scientists analysed the performance of the test in 2,823 people with the disease and 1,254 people without.
It correctly identified when cancer was present in 51.5% of cases, across all stages of the disease, and wrongly detected cancer in only 0.5% of cases.
In solid tumours that do not have any screening options – such as oesophageal, liver and pancreatic cancers – the ability to generate a positive test result was twice as high (65.6%) as that for solid tumours that do have screening options such as breast, bowel, cervical and prostate cancers.
Meanwhile, the overall ability to generate a positive test result in cancers of the blood, such as lymphoma and myeloma, was 55.1%. The test correctly also identified the tissue in which the cancer was located in the body in 88.7% of cases.
Dr Eric Klein, chairman of the Glickman Urological and Kidney Institute at Cleveland Clinic in the US and first author on the research, said: “Finding cancer early, when treatment is more likely to be successful, is one of the most significant opportunities we have to reduce the burden of cancer.
“These data suggest that, if used alongside existing screening tests, the multi-cancer detection test could have a profound impact on how cancer is detected and, ultimately, on public health.”
Dr Marco Gerlinger, from the Institute of Cancer Research in London and consultant medical oncologist at the Royal Marsden NHS foundation trust, said: “This new study shows impressive results for a simple blood test that can detect multiple cancer types.
“False positives are low which is important as this will avoid misdiagnoses. For some of the most common tumour types such as bowel or lung cancer, the test even picked up cancers that were very small, at a stage where many of them could potentially be cured.
“The study was done in patients whose cancer was already diagnosed based on other tests and this screening technology still needs to be tested in actual screening trials before routine use.
“But it already allows a glance at early cancer detection in the future which will almost certainly be built around liquid biopsy tests, which detect cancer DNA in the bloodstream.”
Meanwhile, the results of the NHS pilot of the test, which will include 140,000 participants, are expected by 2023.
Prof Peter Johnson, national NHS clinical director for cancer, said: “This latest study provides further evidence that blood tests like this could help the NHS meet its ambitious target of finding three-quarters of cancers at an early stage, when they have the highest chance of cure.
“The data is encouraging and we are working with Grail on studies to see how this test will perform in clinics across the NHS, which will be starting very soon.”