Bowel cancer screening and cervical cancer screening don’t need to detect a cancer to help save someone’s life.

That’s because they can also pick up changes that are sometimes called “pre-cancers”, where groups of non-cancerous cells show signs that they could lead to cancer over time. By monitoring or treating these altered, potentially “pre-cancerous”, cells, doctors can make sure that bowel and cervical cancers don’t develop in the first place.

We can apply that same thinking much more widely. All cancers develop from healthy cells. Studying pre-cancers helps us understand how and why that happens, and it can point us towards new ways of stopping the process in its tracks.

So, our researchers are working to turn insights about the changes that can precede cancer into new screening tests and even a new generation of vaccines. But there are extra complications that come with trying to stop cancer before it starts. Pre-cancers are hard to define and even harder to spot. If we want to do anything about them, we need to work out exactly what we’re dealing with. 

What is pre-cancer?

Pre-cancerous cells aren’t cancer, and, despite the name, many of them aren’t “pre” anything either. They’re cells with abnormal changes to their shape, size or appearance which can mean they have a higher risk of becoming cancer. But, crucially, that outcome is still unlikely overall.

For one thing, many potentially pre-cancerous changes make cells vulnerable before they make them dangerous – our immune system can spot abnormal cells and either keep them growing or completely clear them out. In fact, the immune system is constantly getting rid of abnormal cells with a higher than average risk of leading to cancer.

Even in the few cases where immune system doesn’t step it, abnormal cells can turn into cancer so slowly that they’ll never cause a problem in someone’s lifetime. Again, that’s if they ever do at all – many cells with potentially pre-cancerous changes go back to normal on their own.

That all goes to highlight the complexities of finding and treating pre-cancer directly. On the one hand, things we could label pre-cancers are quite common, and most aren’t ever going to cause any harm, so treating them could create more problems than it’s likely to solve. On the other hand, if we can develop simple ways of finding and dealing with the few pre-cancers that create the highest risk, we have a huge opportunity to stop cancers in their tracks – long before people need to feel their effects.

That brings us to screening, which all about finding the right balance.

Pre-cancer, cancer screening and the capsule sponge

Bowel screening and cervical screening help illustrate how a screening programme needs to perform.

Bowel screening can identify potentially pre-cancerous bowel polyps. Doctors can remove almost all of those with the same tool they use to look inside the bowel. It’s a relatively simple procedure and it comes with the benefit of helping prevent more cases of one of the UK’s most common cancers.

Cervical screening can find potentially pre-cancerous changes that sometimes develop in cervical cells infected with high-risk strains of human papillomavirus (HPV). Doctors can then look at a sample of those cells under the microscope and recommend either monitoring or treating them, depending on how abnormal they are. That makes it possible to choose the best way forward every time cervical screening identifies abnormal cervical cells.

We’re now funding a trial to see whether something as apparently simple as a pill on a thread could support a similarly effective screening programme for oesophageal cancer, which starts in the food pipe that connects the mouth and the stomach. Together, the capsule sponge and its accompanying lab test can identify another potentially pre-cancerous condition called Barrett’s oesophagus in people with persistent heartburn. 

As we mentioned above, the immune system is usually able to do this on its own. The vaccines just give immune cells a little extra guidance, which can be especially important when people have a higher cancer risk. In people who smoke, for example, or who have inherited gene changes that restrict a cell’s ability to repair DNA damage (like BRCA mutations), there are more chances for pre-cancers to grow and progress without the immune system stopping them.

Across all three Vax projects researchers are using technology used in COVID-19 vaccines to give the immune system a clear set of genetic instructions that should help it to spot and kill more potentially pre-cancerous cells. That’s possible because early DNA changes that can raise the risk of a cell becoming cancerous also lead to “red flag” proteins called neoantigens appearing on the cell’s surface. As pre-cancers become cancers, they develop ways of disguising these changes, but, before then, a well-designed vaccine is likely to be much more effective.  

We recently announced more than £2m of funding for a phase 1 clinical trial of LungVax, which will help us understand the best and safest dose to use to help protect people at high risk of lung cancer. Later stages of the trial will focus more on how well the vaccine works. The first participants should receive their first doses in summer 2026.

Starting with prevention

OvarianVax, LungVax and LynchVax are examples of precision cancer prevention projects, which turn insights about specific people’s cancer risk into tools we can use to protect them.

Elsewhere, Professor Sarah Blagden, one of the co-leads for LungVax, is leading the MILI trial for people with a genetic condition called Li Fraumeni syndrome, which gives them a higher cancer risk than any other group. MILI is testing whether a diabetes drug called metformin can help keep cells with faulty “tumour suppressor” genes from picking up other changes that could lead to cancer. It has the potential to help us design specific cancer-preventing drugs that do metformin’s job more effectively.

Our researchers have also shown that taking a small dose of aspirin every day can halve bowel cancer risk for people with Lynch syndrome. It’s likely the immune system is involved in that effect too, as aspirin reduces inflammation, a different type of immune response that helps wounds heal, but can sometimes support the development of potentially pre-cancerous cells. 

These are all layers of pre-cancerous complexity that our researchers are only just starting to unpeel. But, as they do so, we’re learning that cells have to go through multiple transitions – and get past multiple layers of defences – before they can even get close to causing cancer. Everything we find out about that process presents us with an opportunity to make a life-saving difference.