NHS launches world's largest trial of Galleri blood test to detect 50+ cancer types early

The NHS is launching the world's largest trial of a blood test that can identify more than fifty types of cancer before a person feels sick. Starting this week, thousands of volunteers will give blood samples at mobile clinics scattered across eight regions of England. The test, called Galleri, works by detecting chemical changes in fragments of DNA that tumors shed into the bloodstream long before symptoms would ever appear. It represents a fundamental shift in how the health service might catch the disease—not when patients come to their doctors with complaints, but years earlier, when treatment is most likely to work.

The trial aims to recruit 140,000 people aged fifty to seventy-seven from different backgrounds and parts of the country. Participants will visit a mobile clinic to give an initial blood sample, then return after twelve months and again at two years to provide additional samples. The NHS is deliberately casting a wide net across Cheshire and Merseyside, Greater Manchester, the North East, the West Midlands, the East Midlands, the East of England, Kent and Medway, and South East London. Letters are being sent inviting people to participate, though anyone who has received a cancer diagnosis in the past three years is excluded from the study.

The Galleri test has already shown promise in research published this summer. Scientists studied how it performed in nearly 2,800 people with cancer and over 1,200 without. The test correctly identified cancer in just over half of all cases across all disease stages. More importantly, it wrongly flagged cancer in only 0.5 percent of people who did not have the disease—a remarkably low false positive rate. For cancers that are notoriously difficult to catch early, like pancreatic, liver, and esophageal tumors, the test's accuracy nearly doubled compared to cancers already covered by existing NHS screening programs. When it came to identifying where in the body the cancer was located, the test pinpointed the correct tissue in nearly 89 percent of cases.

The trial design itself is rigorous. Half the participants will have their blood tested immediately with Galleri. The other half will have their samples stored and may be tested later. This split allows researchers to directly compare how many cancers are caught at an early stage in each group, and whether early detection through this test actually leads to better outcomes. Anyone whose sample suggests possible cancer will be contacted by a trial nurse and referred to an NHS hospital for further investigation. The first results are expected by 2023.

Amanda Pritchard, the NHS chief executive, framed the trial as a potential turning point. She said the test could mark the start of a revolution in how cancer is detected and treated, both in Britain and globally. The NHS has set an ambitious goal to catch three-quarters of all cancers at an early stage, when they are easier to treat and survival rates are higher. If Galleri proves successful in this trial, the health service plans to expand testing to one million additional people in 2024 and 2025. Health Secretary Sajid Javid called the test revolutionary, noting that early diagnosis can save lives and help reduce the number of people needing treatment for advanced cancer.

The trial is being led by Cancer Research UK and King's College London's Cancer Prevention Trials Unit, working with Grail, the company that developed the test. Grail's president in Europe emphasized that the test can detect a wide range of cancer types and predict their location with high accuracy, while maintaining a very low false positive rate. Professor Peter Sasieni, one of the trial's lead investigators, acknowledged that not all screening approaches work equally well, but expressed optimism that Galleri could be a game-changer for early detection. He stressed the importance of studying the test carefully to determine whether it can significantly reduce the number of cancers diagnosed at a late stage.

It is important to note what Galleri does not do. It does not replace existing NHS screening programs for breast, cervical, and bowel cancer, which remain the standard of care. The test also does not detect all cancers. In the US, where it is already available, it has been recommended primarily for people over fifty who face higher cancer risk. The NHS is being cautious and methodical, gathering evidence before making any broader claims. Anyone experiencing symptoms of cancer is still urged to see their GP immediately rather than wait for a blood test result.