Heavy yesteryear smokers, even though they have quitted smoking now, face high risk of developing lung cancer, because some genes have been permanently damaged, reveals a study by the scientists at the B.C. Cancer Agency.

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, articulates the study published Wednesday in the online journal BMC Genomics.

According to Dr. Wan Lam, one of the scientists involved in the study, about 50 % of patients diagnosed with lung cancer are former smokers, and that the study results could one day help scientists repair damaged genes in the lungs.

Lam said, “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 reckons that 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.

The study included the lung tissue of 24 current, former and non-smokers, and using a technique called serial analysis of gene expression (SAGE), the researchers identified almost 600 genes that were different between current and non-smokers. They 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 study unveiled that, of the 600 genes identified, changes in almost one-third of them are irreversible in former smokers. However, this doesn’t send the message that someone who's been using tobacco for years shouldn't quit their habit.

Lam said that continuous smoking would only accumulate the damage to genes that are vital to cell function.

He said, “The main message is don't start smoking if you're not a smoker; lung cancer is one of the most deadly diseases, with one of highest mortality rates of all cancers."

The B.C. Cancer Agency is getting in participants in another study that focuses on the early detection of lung and bronchial cancer. The main target of the study are the former smokers between the ages of 45 and 74 who have smoked at least a pack a day for 30 years.