These findings appear in an article on familial lung cancer in the first issue for January 2006 of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.

(The screening test, spiral computed tomography, uses a 360-degree X-ray beam, along with computer production of image "slices," to highlight lesions in organs and tissues.)

Ann G. Schwartz, Ph.D., of the Karmanos Cancer Institute in Detroit, Michigan, along with an associate, emphasized that 85 to 95 percent of all lung cancers are attributable to cigarette smoking. The rate of lung cancer in the U.S. has dropped over the past two decades as a result of extraordinary personal and public health smoking cessation efforts. Yet, an estimated 46 million former smokers in America remain at risk for the disease, along with almost 49 million who continue to smoke. Consequently, further efforts need to be made to identify high-risk populations.

"Because cigarette smoking is such an overwhelming risk factor and preventable, the importance of family history and genetic susceptibility to lung cancer risk has been overlooked," said Dr. Schwartz.

She pointed out that individuals with a family history of lung cancer are at approximately a two- to threefold increased risk of developing the illness.

In one screening study, at least one first-degree relative had lung cancer in almost 14 percent of the 26,000 patients diagnosed with the disease.

The authors noted that the median age of onset for younger family members affected by lung cancer was 50 , showing a trend toward an earlier age at onset.

"Although evidence pointing to a gene for lung cancer is substantial, the problems associated with the conduct of a linkage study in lung cancer are even greater," said Dr. Schwarz. "The average age of lung cancer diagnosis is 70 years and 5-year survival after diagnosis continues to be poor, at 15 percent, so affected family members are typically deceased, as are their parents, siblings and spouses."

Dr. Schwartz noted that the gene linkage studies conducted to date have been relatively small. Moreover, the regions identified were large showing numerous genes. She also said that many of the regions identified did not overlap exactly between the studies.

"While debate continues about the efficacy of spiral computed tomography screening for lung cancer in broad population of smokers, the ability to focus screening efforts in a truly high-risk subpopulation would clearly be of benefit now," said Dr. Schwarz.

One way the authors suggest to identify high risk groups is to routinely collect data on family history of lung cancer in patients who have chronic obstructive pulmonary disease (COPD), an illness that is also strongly associated with cigarette smoking. In addition, data on family history of COPD should be gathered from those already diagnosed with lung cancer.

Finally, the investigators encouraged the funding of larger linkage and association studies to identify genes for both lung cancer and COPD.

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