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One in four smokers who carry a gene mutation found in two per cent of the population will develop lung cancer, a large-scale study has shown.
The defective gene, known as BRCA2, has long been linked to breast and ovarian cancers.
Scientists found that a specific flaw in the gene almost doubles the overall risk of lung cancer.
A quarter of smokers, who generally have a 13 per cent life-time risk of lung cancer, were predicted to develop the disease if they had the mutation.
If smokers carry BRCA-2 mutations then their lung cancer risk increases from 15 per cent – the risk that smokers already face – to 25 per cent over the course of their lifetime, the medical researchers found.
The study, published in the journal Nature Genetics, compared the DNA of 11,348 Europeans with lung cancer with 15,861 people who were free of the disease. The scientists found a BRCA-2 defect known as c.9976T increased the risk of developing lung cancer by about 1.8 times – on top of the risks from smoking.
This means that about a quarter of smokers who carry the BRCA-2 defect will develop lung cancer at some point in their lives.
“Smokers in general have nearly a 15 per cent chance of developing lung cancer, far higher than in non-smokers,” said Professor Richard Houlston of the Institute of Cancer Research in London.
“Our results show that some smokers with BRCA-2 mutations are at an enormous risk of lung cancer – somewhere in the region of 25 per cent over their lifetime,” Professor Houlston said.
A family of drugs known as the PARP inhibitors have shown some success in treating people with BRCA mutations who have developed breast or ovarian cancers. It is not known yet whether the same drugs are likely to work on lung cancer patients with similar mutations, the researchers said.
Lung cancer kills more than a million people worldwide each year and it is by the far the biggest cancer killer Britain, Professor Houlston said.
“We know that the single biggest thing we can do to reduce death rates is to persuade people not to smoke, and our new findings make plain that this is even more critical in people with an underlying genetic risk,” he said.
Agencies/Canadajournal
