While most people who develop lung cancer have been smokers, scientists have been perplexed for years why some non-smokers develop the disease. About 15 percent of lung cancers occur in lifetime never/non smokers.
A recent study has begun to find out the answers to this dilemma.
Risk factors for lung cancer in people who have never smoked are poorly understood, but a new study from MD Anderson Cancer Center, one of the premier cancer centers in North America, demonstrated that poor DNA repair capacity is an important predictor of lung cancer risk in never smokers.
People who have never smoked, but whose cells cannot efficiently repair environmental insults to DNA, are at higher risk of developing lung cancer than those with effective repair mechanisms. These nonsmokers with suboptimal DNA repair capacity (DRC) are almost twice as likely to develop lung cancer, compared with nonsmokers with normal DRC.
Even more interesting, participants with the lowest ability to repair their DNA had a more than a threefold increased risk, compared with individuals with efficient DRC.
A well established risk factor is secondhand smoke exposure. In participants with inefficient DRC who also reported such exposure, the risk of lung cancer was almost fourfold, a nasty combination of risk factors!
Although the research team has not pinpointed the gene or genes that cause suboptimal DRC, the data suggests that the trait is heritable to some degree. Immediate relatives of those with lowest DRC were 2.5 times more likely to develop lung cancer than were immediate relatives of people with efficient DRC.
Many people think they aren't at risk for lung cancer because they don't smoke, but anyone who has non-smoking relatives who developed lung cancer should probably avoid not just tobacco smoke, but all the other carcinogens and mutagens that are products of combustion.