Could tears hold the key to detecting brain tumours earlier?

Tears can be a sign of sadness, joy and relief. But what if they could also help save lives?

Our scientists believe these tiny drops of fluid may hold vital clues about what’s happening deep inside the brain and could one day help doctors detect brain tumours earlier. 

At the University of Manchester, Professor Petra Hamerlik is leading pioneering research funded through our Stand Up to Cancer campaign to explore this surprising idea.  

A window into the brain 

Early findings suggest that changes in tear fluid could offer an extraordinary window into the brain, potentially helping to diagnose a disease that’s notoriously difficult to detect. 

“Brain tumours are often detected late because their symptoms are vague,” says Professor Hamerlik. “A headache or seizure might be the first sign. Most of the time, it’s just a bad headache, not a tumour. But when it is a brain tumour, the delay in diagnosis can cause huge anxiety for patients and affect their quality of life.” 

Hamerlik knows this all too well. She lost her father to a brain tumour after more than a year of uncertainty.

‘’I don’t want anybody else to go through that anxiety, because I know what we have been through, what my father went through,’’ she says. This deeply personal experience has motivated her to find a better way to diagnose brain tumours.  

The brain’s hidden barrier 

Scientists are exploring all kinds of ways to detect cancers earlier, like analysing bodily fluids for for biological clues. Some cancers shed cells or fragments of DNA into the blood, saliva or even urine and researchers are developing tests to help pick up these signs.   

But the brain presents a unique challenge. It’s protected by the blood–brain barrier, a biological shield that acts as a filter to keep harmful substances out. Crucially though, it also traps much of what’s inside. That makes it harder for doctors to find the biological clues they need to understand what’s happening in the brain.

By the time tumour material escapes into the bloodstream in detectable amounts, the cancer has often already advanced.

To find brain tumours earlier, scientists need to look elsewhere 

Why tears? 

Tears do more than express emotion. They deliver oxygen and nutrients to our eyes, remove waste and protect against infection. But that’s not all, they also contain a wealth of biological information. 

Professor Hamerlik’s team turned to tear fluid because of the close connection between the eyes and the brain. The optic nerve links directly to the brain, and tears are made from blood plasma filtered through glands controlled by the brainstem.

These glands also produce immune comments vital to eye health. That made the team wonder whether tear fluid could be affected by immune changes in the brain.  

“We hypothesised that as a tumour develops, it reshapes the immune system in the brain and that this could be reflected in tear fluid,” she says.  So, she and her team set out to develop a test that could measure these immune changes.

From pilot study to potential GP tool 

It takes a long time to turn an innovative idea into something that could actually benefit patients. In fact, Hamerlik has been working on this project for over 10 years.

She started in 2012. Three years later, once the team had optimised the analytical techniques, she started the first clinical study – a Danish proof-of-concept study involving 164 participants, including healthy volunteers and people with brain tumours. 

The results were promising. 

“By collecting tears using a standard eye Schirmer strip test already used for dry eye disease, we found we could detect brain tumours with high accuracy,” says Hamerlik. 

A decade on, with more biological insights and funding from Stand Up To Cancer, the team are running a large NHS-approved validation study called INFORM. It’s recruiting patients from across the UK, Sweden, Germany, Greece, Slovakia and the Czech Republic to see if the tear test can reliably detect brain tumours in a larger group.