BC Scientists Say Smokers Who Quit Years Ago Still at Higher Risk of Lung Cancer

By CAMILLE BAINS

VANCOUVER (CP) – Research by scientists at the B.C. Cancer Agency suggests heavy smokers who butt out years ago still face a high risk of developing lung cancer because some genes have been permanently damaged.

A study published Wednesday in the online journal BMC Genomics says that’s the case even though other genes in the lungs of former smokers return to levels similar to those in people who’ve never puffed.

Dr. Wan Lam, one of the scientists involved in the study, said about 50 per cent of patients diagnosed with lung cancer are former smokers and that the study findings could one day help scientists repair damaged genes in the lungs.

“We’re identifying the functions that are being disrupted in the lungs so this gives scientists and clinicians a starting point to look at how to deal with this issue, how to repair these problems,” Lam said.

Lam said gene therapy may be years away but it’s a possibility because unlike other organs in the body, the lungs are accessible for treatment with inhalers and bronchoscopes, for example.

For the study, researchers looked at the lung tissue of 24 current, former and non-smokers.

Using a technique called serial analysis of gene expression (SAGE), they identified almost 600 genes that were different between current and non-smokers.

Scientists found that only about a fifth of the genes in a cell are switched on at any given time, but environmental factors like smoking lead to changes in gene activity.

The research showed that of the 600 genes identified, changes in almost one-third of them are irreversible in former smokers.

But that doesn’t mean someone who’s been using tobacco for years shouldn’t quit their habit. Continued smoking would only accumulate the damage to genes that are vital to cell function, Lam said.

“The main message would be don’t start smoking if you’re not a smoker,” he said.

“Lung cancer is one of the most deadly diseases, with one of highest mortality rates of all cancers.”

The B.C. Cancer Agency is also enrolling participants in another study that focuses on the early detection of lung and bronchial cancer.

Former smokers between the ages of 45 and 74 who have smoked at least a pack a day for 30 years are the main target of the study.