Genes Influence Lung Cancer Risk

But smoking still plays dominant role, researchers add

TUESDAY, Dec. 21, 2004 (HealthDayNews) -- The basic medical warning about the dangers of smoking is especially important for anyone with a relative, however distant, who has had lung cancer, a new Icelandic study shows.

The risk of lung cancer is 2.7 times higher for someone with a parent who had lung cancer; about double for those with a sister, brother or child with the malignancy; one third higher when an uncle or aunt had the disease; and 14 percent higher for a cousin of a lung cancer patient, said the report.

But "it should be emphasized that tobacco smoke plays a dominant role in the pathogenesis of this disease, even among those individuals who are genetically predisposed to lung carcinoma," the report said.

It appears in the Dec. 22/29 issue of the Journal of the American Medical Association.

Although other studies have indicated genetics might play a part in lung cancer, this latest research provides the most solid evidence yet because Iceland's unusually complete database contains information on all living residents and most of their ancestors.

The study was done by physicians at the Landspitali-University Hospital in Reykjavik, in collaboration with deCODE Genetics, a small biopharmaceutical company based in that city. The company works on finding genetic characteristics underlying various diseases and using that information to develop better treatment and preventive strategies.

The next step in the case of lung cancer is to identify the genes responsible for the increased risk, said Dr. Kari Stefanssoon, chief executive officer of deCODE. Studies are under way and "we will have them for you next year," he said.

What the new study shows, he said, is that "lung cancer has a very significant genetic component. There is a genetic variant that creates vulnerability to something like tobacco smoke. If they smoke, these people have two strikes against them."

The study looked at the incidence of lung cancer in relatives of all 2,756 Icelanders diagnosed with lung cancer between 1955 and 2002. "The nationwide genealogical database used in our study provided a means for uncovering the familial component by revealing more connections between patients, missed in most other populations," the researchers wrote.

Identifying the specific genes that increase lung cancer risk could lead to screening programs that add an edge to anti-smoking efforts, Stefanssoon explained. "Once you know you have a genetic predisposition, you should be told that you have an option not to smoke, and that not smoking may help prevent that genetic predisposition from turning into a disease," he said.

Another report in the same issue of the journal found another factor that increases risk of lung cancer: high levels of arsenic in drinking water.

Physicians at National Taiwan University said that people whose water had the highest levels of arsenic had more than a threefold higher risk of lung cancer than those with the lowest level of exposure.

But that study also emphasized the overwhelming role that smoking plays in the disease. Among participants with the lowest arsenic exposure, smokers had four times the risk of lung cancer than nonsmokers. The risk was increased 11-fold for smokers with the highest levels of arsenic exposure, compared to nonsmokers with the lowest arsenic exposure.

More information

A tool for assessing the risk of lung cancer is provided by Memorial Sloan-Kettering Cancer Center.

SOURCES: Kari Stefenssoon, M.D., Ph.d, chief executive officer, deCODE Genetics, Reykjavik, Iceland; Dec. 22/29, 2004, Journal of the American Medical Association
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