Mayo Clinic researchers are reporting that the risk of developing lung cancer becomes twofold for people having a common genetic disorder regardless of whether they are smokers or not.
Writing about their findings in the Archives of Internal Medicine, a journal published by the American Medical Association, the researchers said that the genetic disorder alpha-1 antitrypsin deficiency (?N1ATD) could explain up to about 12 percent of lung cancer patients in this study, and likely represents the same widespread risk in the general population.
"This is a seriously under-diagnosed disorder and suggests that people who have lung cancer and chronic obstructive pulmonary diseases (COPD) in their families should be screened for these gene carriers," says Dr. Ping Yang, a Mayo Clinic epidemiologist and lead investigator on the study.
Referring to figures from the World Health Organization, she pointed out that at least 120 million people worldwide were carriers of this genetic disorder.
She also said that her team's study showed that the disorder "is among the highest for major gene effects on the risk of a common cancer."
"It has been suspected that ?N1ATD increased susceptibility to lung cancer, but this is the first solid evidence that supports and quantifies this risk," says Dr. Yang.
During the study, the research team looked at 1,443 patients with lung cancer treated at Mayo Clinic from 1997 to 2003, a control group of 797 residents in the community, and a second control group of 902 siblings of the lung cancer patients.
The researchers found that the ?N1ATD carrier rate among 1,443 genotyped patients with lung cancer was 13.4 percent, compared to 7.8 percent among unrelated control participants.
They also observed that all ?N1ATD carriers were at a similarly greater risk of developing lung cancer, regardless of smoking status.
According to them, increased lung cancer risk among such people is independent of a family history of lung or other cancers.
She recommended routine lung function check-ups for ?N1ATD carriers, and suggested that such people avoid potential lung carcinogens.
"We found people who carry these genes are more vulnerable to carcinogen-containing tobacco smoke, even second-hand smoke, than non-carriers," says Dr. Yang.
Dr. Yang, however, made it clear that though her study helped explain why people who have never smoked can develop lung cancer, it did not mean that people without the gene would not develop lung cancer.
"Smoking remains the overwhelming risk factor for lung cancer development," she said.