Danish scientists have created a new form of blood test that predicts a person’s chance of developing lung cancer. 

Developed by a team of researchers from the University of Copenhagen, Copenhagen University Hospital and the University of Bristol, the blood test measures the amount of a specific type of DNA mutation associated with smoking.

Chemicals present in cigarette and cigar smoke interact with cell DNA causing a process called demethylation, resulting in the usual structure of DNA changing.

This change in structure can affect how specific genes are expressed, resulting in less, more or an altered version of a specific cell protein – all of which can result in cancer.

Through previous research, the team had identified a gene that is commonly altered through smoking called AHRR (Aryl-Hydrocarbon Receptor Repressor).

Upon exposure to smoke carcinogens, AHRR becomes demethylated and reverts very slowly back to its normal state once a person quits smoking, meaning altered AHRR remain measurable for a long time.

The team developed a method to measure the amount of AHRR demethylation in cell DNA collected from blood samples.

Looking at blood samples taken from 9,234 people who took part in the Copenhagen Heart Study (around 7,000 of which were smokers), the team compared methylation levels to Danish health registers to determine who had subsequently developed lung cancer.

The team discovered a clear correlation between AHRR demethylation and risk of lung cancer.

“We report about a more precise way of identifying patients at high risk of developing lung cancer than the methods in use today. Lung cancer screening is currently not offered in Denmark, but in the future, we can target lung cancer screening towards smokers and ex-smokers that actually have a high risk of developing the disease,” said co-author Stig Bojesen, a clinical professor in the Department of Clinical Medicine at the University of Copenhagen, Denmark.

The new blood test offers a simple form of lung screening for Denmark and perhaps the rest of the world, based on further evidence of its accuracy and effectiveness. Rather than relying on answers to questionnaires, doctors could use the test to determine which patients were at a high risk of lung cancer and in need of a follow-up CT scan to catch any potential early-stage cancers.

Interestingly, the new blood test has already received some criticism, with Niels Them Kjaer of the Danish Cancer Society claiming that it complicates a process that should be simple: “It’ll be much easier to identify risk groups by asking them about their current and former smoking, and we can also measure people’s lung age, which also tells us something about their risk of developing lung cancer, regardless of whether they are smokers or ex-smokers.”

Nevertheless, the team are insistent of the test’s advantages over current standard screening methods.