Lung cancer may run in families

Individuals with a mother, sister or other "first-degree" relative with lung cancer are at increased risk of developing the disease, regardless of whether they smoke. Researchers say the finding supports the role of genetics and perhaps a shared environment in the development of lung cancer.

lung cancer tops the list of the most common cancers worldwide. Tobacco smoking is undeniably the major causative factor, with long-term smokers having a 10-fold higher risk of the disease than nonsmokers.

Other recognized risk factors for lung cancer include exposure to radiation, asbestos and heavy metals such as arsenic, chromium and nickel.

Environmental and genetics factors are also increasingly thought to play a role. It has "long been postulated," UK-based researchers explain in the International Journal of Cancer, that people may differ in their susceptibility to environmental risk factors and evidence is growing for a familial risk pattern.

To further investigate clustering of lung cancer within families, Dr. Athena Matakidou from the Institute of Cancer Research in Surrey and colleagues researchers analyzed family history data on 1,482 female lung cancer cases and 1,079 similar but unaffected female "controls."

The investigators found a 49 percent increased risk of lung cancer among women who had a first-degree relative with the disease. The link remained even after factoring in age and cigarette smoking.

The risk is even greater with early-onset lung cancer and with multiple affected family members.

Lung cancer usually occurs because some outside factor, called a carcinogen, has triggered the growth of abnormal, cancerous cells in the lung. These cancerous cells multiply out of control and eventually form a mass called a tumor. As the tumor grows, it destroys nearby areas of the lung. Eventually, the tumor's abnormal cells can spread (metastasize) to nearby lymph nodes and to distant organs, such as the brain. In most cases, the carcinogens that trigger lung cancer are chemicals found in cigarette smoke.
Women with a first-degree relative who developed lung cancer before 60 years of age had about a twofold higher risk of developing the disease while those having two or more relatives with lung cancer had a greater than twofold increased risk.

The current study "is consistent with a genetically determined risk as we have found further elevation of the lung cancer risk with earlier age of onset of the disease and with multiple affected family members," the investigators note in their report.

"These findings," they add, "support the hypothesis that genetic susceptibility to lung cancer might act as both an independent risk factor and an effect modifier of environmental risk factors."