Years before the tumour: the immune 'fog' a UCL team says it can now see
What happened
Scientists at University College London (UCL) say they have spotted an early warning sign of lung cancer that appears long before a tumour does. Their study was published in the journal Nature. UK Research and Innovation announced it on 8 October 2026. Cancer Research UK wrote about it the day before. The paper is called 'A preinvasive regulatory T cell axis for lung cancer interception'. The work was led by Associate Professor James Reading and Professor Sam Janes at UCL. It was paid for by Cancer Research UK and the Medical Research Council, with support from the National Institute for Health and Care Research and other partners. The team looked at blood and tissue samples from people already taking part in long-running lung screening and surveillance studies. They found that a particular kind of immune cell, called a regulatory T cell, built up months or even years before cancer appeared. Regulatory T cells, or Tregs for short, are supposed to calm the immune system down. They stop it attacking healthy parts of the body. But the UCL team thinks that in the lungs, a build-up of these cells acts like a fog. It hides very early, pre-cancerous cells from the immune system that should be clearing them away. The researchers also tested a drug in mice. In mice that already had pre-cancerous lung cells, the drug reversed that calming effect. Only half as many of the treated mice went on to develop lung tumours. None of them developed large tumours.
Why this matters
Lung cancer is one of the hardest cancers to treat well, mainly because it is so often found late. Cancer Research UK says about 50,200 people are diagnosed with lung cancer in the UK each year. UK Research and Innovation puts the number of deaths at around 32,800 a year, and says only about 11.1% of people diagnosed are expected to live 10 years or more. The stage at which it is found changes everything. According to Cancer Research UK, more than 6 in 10 people diagnosed at stage 1 survive at least five years. Fewer than 1 in 10 do when it is found at stage 4. That is why so much effort now goes into finding cancer earlier. This study goes a step further. It asks whether you could spot the risk before there is any cancer at all, and then step in. Professor Sam Janes described the shift like this: the field is "moving from the current status quo of largely treating cancer when it develops" towards tackling the disease while it is still pre-cancerous. Dr James Reading put the goal plainly. He said the team wants "an early warning system to detect lung cancer before that cancer is fully fledged". He also said: "We urgently need new ways to prevent lung cancer in people at high-risk of developing the disease."
What the evidence actually says
It is worth being clear about what has and has not been shown. The Treg finding comes from real human samples. The team saw the same pattern in people taking part in lung screening programmes and in mouse models. Dr Reading said the timing surprised them. He noted that the team "never anticipated that they were coming on very intensely super early on". The blood test is a prototype. It is not something your GP can order. The team is still refining it, and is using artificial intelligence tools to help find the pattern. Dr Reading said that "pattern recognition across billions of data points is not something that the human brain" does well. The drug results are from mice, not people. Halving the number of animals that developed tumours is a striking result in a laboratory. It is not the same as a result in humans. The team says it is working towards a clinical trial. The funders were measured too. Charlotte Durkin of the Medical Research Council said the study "provides valuable new insight into the early stages of lung cancer development". Catherine Elliott of Cancer Research UK said the work "is helping lay the foundations for more personalised approaches to cancer prevention, detection and interception". Note the words: insight, foundations. This is an important early step, not a treatment you can ask for.
Practical advice
Nothing in this study changes what you can do today. But the things that already work still matter, and they matter more if you are in a higher risk group. If you smoke, stopping is still the single biggest thing you can do for your lungs. Your local stop smoking service and your pharmacist can both help, and NHS support is free. If you are aged 55 to 74 and you smoke or used to smoke, you may be invited to an NHS lung health check in England. If you get a letter, go. Take-up is what makes these programmes work. Watch for symptoms that do not settle. A cough that lasts three weeks or more, coughing up blood, breathlessness that is new for you, chest or shoulder pain, repeated chest infections, losing weight without trying, or feeling very tired. None of these means cancer. All of them are worth a GP appointment. Do not wait because you feel silly. GPs would far rather see ten people with a harmless cough than miss one. If you have been offered a clinical trial, or you are curious about research in your area, you can ask your specialist team or search the NHS 'Be Part of Research' service.
What to know
A UCL team has found that a type of immune cell, the regulatory T cell, builds up in blood and lung tissue months or years before lung cancer appears. They think it hides very early cancer from the immune system. A prototype blood test could one day flag who is at rising risk. A drug tested in mice halved the proportion that went on to develop tumours and prevented all large ones. This is early-stage science. The blood test is a prototype and the drug has only been tested in animals. But it points towards a future where lung cancer might be stopped before it starts, rather than treated after it arrives. For now, the best protection is the ordinary kind: stop smoking if you smoke, go to your lung health check if you are invited, and get a stubborn cough looked at. Sources: UK Research and Innovation, 'Clearing "immune fog" could stop lung cancer before diagnosis', 8 October 2026, https://www.ukri.org/news/clearing-immune-fog-could-stop-lung-cancer-before-diagnosis/; Cancer Research UK News, 'Could clearing "immune fog" stop lung cancer?', 7 October 2026, https://news.cancerresearchuk.org/2026/10/07/could-clearing-immune-fog-stop-lung-cancer/; LabMedica, 'Blood-Based Immune Signal Could Reveal Lung Cancer Risk Before Tumors Develop', October 2026, https://www.labmedica.com/immunology/articles/294813764/blood-based-immune-signal-could-reveal-lung-cancer-risk-before-tumors-develop.html This article is for general information and does not replace advice from a doctor, pharmacist or other qualified healthcare professional.
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