Genetic predisposition to lung cancer exists

First-degree relatives of black individuals with early-onset lung cancer have twice the risk of lung cancer than first-degree relatives of white individuals with early-onset lung cancer, according to a study in the June 22/29 issue of JAMA.

Cigarette smoking has long been established as the major risk factor for lung cancer in the general population, according to background information in the article. However, familial aggregation of disease (the concentration of cases of a disease in families), has also been identified as a risk factor. Greatest risk is seen in families with early-onset disease (less than 50 years at diagnosis) compared with those whose onset of lung cancer occurred at older ages. Researchers have determined that genetic predisposition to lung cancer exists. Approximately 173,770 new diagnoses of lung cancer were estimated to have occurred in the U.S. in 2004. Early-onset cases represent 6.7 percent of lung cancers diagnosed in the U.S.

Michele L. Cote, Ph.D., of Wayne State University, Detroit, and colleagues conducted a study to estimate the lifetime risk of lung cancer by race, smoking status, and family history of early-onset lung cancer. This information could be used to identify high-risk individuals and to counsel families with a history of early-onset lung cancer.

The researchers analyzed data from incident cases and controls that occurred between 1990 and 2003 in metropolitan Detroit. The study included 7,576 biological mothers, fathers, and siblings of 629 early-onset cases and 773 controls. One-third of the population was black.

The researchers found that relatives of black patients with early-onset lung cancer had more than twice (2.07) the risk of lung cancer compared with relatives of white patients with early-onset lung cancer after adjusting for age, sex, pack-years, pneumonia, and chronic obstructive lung disease.

"This finding could be the result of a higher degree of underlying susceptibility or aggregation of unmeasured risk factors for lung cancer in black families," the authors write.

The researchers also found that smokers with a family history of early-onset lung cancer in a first-degree relative had a higher risk of developing lung cancer with increasing age than smokers without a family history. An increase in risk occurs after age 60 years in these individuals, with 17.1 percent of white case relatives and 25.1 percent of black case relatives diagnosed with lung cancer by age 70 years.

"Family history assessment should be included when evaluating smokers or those presenting with symptoms consistent with lung disease. Further characterization of high-risk individuals is important to provide clinicians with counseling tools and to enhance the effectiveness of screening programs. Family history of early-onset lung cancer in a first-degree relative should be considered a risk factor in other relatives older than 18 years. As knowledge about risk factors (other than tobacco use) for lung cancer increases, physicians may be more likely to consider lung cancer as a differential diagnosis in their young patients. Earlier diagnosis and intervention may reduce mortality and morbidity in this population. Ongoing trials should evaluate the usefulness of screening modalities among those with a family history of early-onset lung cancer."