Most cases of lung cancer are caused by smoking, and now a new test could warn smokers if they are likely to develop the disease.
Scientists have discovered that cells taken from the mouth and nose react differently to infrared light in people vulnerable to lung cancer.
"Tobacco smoke exposure seems to cause a different type of injury to cells in those that go on to develop lung cancer," said Professor Sam Janes from University College London.
"If we can use this detection system early enough maybe we can spot lung cancer at a much earlier stage or even inform whether an individual is at risk of lung cancer.
"Our study, using infrared light to examine such cells for the first time, revealed that the cells of smokers with lung cancer could be differentiated from those without lung cancer with an accuracy of 80%."
The scientists studied samples from 76 smokers, half of whom had been diagnosed with lung cancer.
Previous research had shown that the way very pure light generated by a synchrotron particle accelerator is scattered by human cells may indicate the presence of the disease.
Further work showed that infrared light can produce the same results in a laboratory setting.
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Prof Janes added: "Our vision for the future is that smokers could get a test in the GP or pharmacy, swab their mouth or nose, and the sample is then sent off for analysis.
"The earlier lung cancer is detected, the better the outcome."
The research was presented at the British Thoracic Society's Winter Meeting in London.
Next the scientists plan to analyse samples from a larger population and monitor participants over time to see how many develop lung cancer.
The results could help identify which patients should be referred for CT (computed tomography) X-ray scans.