Thousands of people will take part in an NHS trial of a simple blood test that can detect more than 50 types of cancer before symptoms appear.
The Galleri test, currently available in the US, can detect cancers not routinely screened for and can pinpoint where in the body the disease is coming from with a high degree of accuracy, according to The Telegraph.
The test works by looking for chemical changes in fragments of genetic code – cell-free DNA (cfDNA) – that leak from tumours into the bloodstream. Some cancerous tumours shed DNA into the blood a long time before a person experiences symptoms.
The Galleri test does not detect all cancers or replace NHS screening programmes, like those for breast, cervical and bowel cancer. In the US, it is recommended for people at higher risk of cancer, including over-50s.
Mobile testing clinics
As part of the NHS trial, which is the worldʼs largest, blood samples will be taken at several mobile testing clinics in retail parks and other community locations. The NHS aims to recruit 140,000 volunteers in eight areas of England to see how well the test works in the health service.
Letters are being sent to people from different backgrounds and ethnicities aged between 50 and 77 asking them to take part. Participants, who must not have had a cancer diagnosis in the past three years, give a blood sample at a local mobile clinic and are then invited back after 12 months, and again at two years, to give further samples.
NHS Chief Executive Amanda Pritchard said: “The Galleri blood test, if successful, could play a major part in achieving our NHS Long Term Plan ambition to catch three-quarters of cancers at an early stage, when they are easier to treat.” The test is particularly effective at finding cancers that are difficult to identify early – like head and neck, bowel, lung, pancreatic and throat cancers.
The NHS trial is being led by the Cancer Research UK and Kingʼs College London Cancer Prevention Trials Unit with Grail, which developed the Galleri test.
Study may be extended
The first results are expected by 2023. If successful, the plans to extend the rollout to a further one million people in 2024 and 2025.
Research published in June in the journal Annals of Oncology found that the test had a very low false positive rate, meaning few people would be wrongly diagnosed with cancer, adds The Telegraph. Scientists analysed how the test worked in 2,823 people with the disease and 1,254 people without. It correctly identified cancer in 51.5% of cases, across all stages of the disease, and wrongly detected cancer in just 0.5% of cases.
When it came to solid tumours that are not currently screened for – such as oesophageal, liver and pancreatic cancers – the ability to generate a positive test result was twice as high (65.6%) as for solid tumours with screening options such as breast, bowel, cervical and prostate cancers. With blood cancers, around 55% of cases were detected, while the test correctly identified the tissue in which the cancer was located in the body in 88.7% of cases.
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