Lung cancer warning sign

Cigarette smokers lessen their chances of getting lung cancer by kicking the habit, but they remain at a higher-than-normal risk for years after quitting. Getting tested for abnormal cell growth in the lung's bronchial passages is one way to identify those at risk for developing lung cancer, but within a year of stopping smoking, such tests lose much of their diagnostic value.

Researchers now report that another test may signal risk in ex-smokers. It uses a protein called Ki-67, which shows up during the proliferation of aberrant cells, including the kind that produces lung tumors.

"Just having Ki-67 doesn't mean a person has cancer," says study coauthor J. Jack Lee, a biostatistician at the University of Texas M. D. Anderson Cancer Center in Houston. "However, it does suggest some abnormality."

The new study reveals that Ki-67 crops up in bronchial tissues of many ex-smokers who don't have lung cancer or even any signs of abnormal cell growth. This suggests that Ki-67 could be a molecular early warning sign of cancer risk, Lee says. As such, Ki-67 could help physicians identify candidates for trials designed to test preventive treatments, he says. The study appears in the July 18 JOURNAL OF THE NATIONAL CANCER INSTITUTE.