Having a relative with lung cancer (search) may more than triple your risk of developing the deadly disease, according a new study.

Although smoking cigarettes or using other tobacco products is the biggest contributing risk to lung cancer risk, researchers say genetics may also play a role.

The study showed that first-degree relatives, such as brothers, sisters, or parents of lung cancer patients were two to 3.5 times more likely to develop lung cancer than the general population.

Lung cancer is the leading cause of cancer death in men and women in many Western countries, including the U.S.

Lung Cancer Risk Among Relatives

In the study, which appears in the Dec. 22/29 issue of The Journal of the American Medical Association, researchers examined the role of genetics in lung cancer risk in the population of Iceland.

The risk for first-, second-, and third-degree relatives of people with lung cancer was estimated by comparing 2,756 people diagnosed with lung cancer in Iceland from 1955-2002, with all living Icelanders.

Researchers also estimated the risk of lung cancer associated with smoking.

The study showed that the increased risk of lung cancer among relatives of lung cancer patients extended beyond the immediate family, although first-degree relatives had the highest risk.

For example, parents of lung cancer patients had 2.7 times increased risk. Siblings and children of lung cancer patients had twice the risk.

Second-degree relatives of people with lung cancer, such as aunts, uncles, and nephews/nieces, were about 30 percent more likely to develop the disease, and third-degree relatives, such as cousins, had a 14 percent higher risk.

Researchers found the risk associated with having a family member with lung cancer was higher if the cancer developed early, before age 60. For relatives of people with early onset cancer, the risk of developing cancer was up to 3.5 times higher.

Although the study indicates that genetics play a role in affecting lung cancer risk, researchers say tobacco smoke still plays the dominant role, even among those who are genetically predisposed to lung cancer.

ByJennifer Warner, reviewed by Michael W. Smith, MD

SOURCES: Johnsson, S. The Journal of the American Medical Association, Dec. 22/29, 2004; vol 292: pp 2977-2983. American Cancer Society.