Urine test may reveal lung cancer risk

Most of us poor smokers like to think we'll be one of the lucky ones who makes it to 100 unscathed. And now researchers think they may soon be able to tell which of us will, through a simple urine test.

Only about one in 10 smokers gets lung cancer. "A history of smoking has always been thought of as a predictor of lung cancer, but it is actually not very accurate," said Jian-Min Yuan, associate professor of public health at the University of Minnesota. "Smoking absolutely increases your risk, but why it does so in some people but not others is a big question."

Researchers collected data from over 80,000 men and women, carrying out in-person interviews to assess levels of cigarette smoking, dietary and other lifestyle factors. They also collected blood and urine samples from more than 50,000 patients.

The nicotine metabolite NNAL had been shown to induce lung cancer in laboratory animals, but the effect in humans hadn't yet been studied. To evaluate its impact, researchers identified 246 current smokers who later developed lung cancer and 245 smokers who did not during the 10-year period following the initial interview and collection of urine samples.

Patients with a mid-range level of NNAL had a 43 per cent increased risk of lung cancer compared with those with the lowest levels, while those at the highest level had more than double the risk of lung cancer, after taking into account the effect of number of cigarettes per day and number of years of smoking.

Levels of nicotine in the urine were also calculated. Those with the highest levels of nicotine and NNAL had eight and a half times the risk of lung cancer compared with smokers who had the lowest levels after accounting for smoking history.

"Smoking leads to lung cancer, but there are about 60 possible carcinogens in tobacco smoke, and the more accurately we can identify the culprit, the better we will become at predicting risk," said Yuan.

The results were presented at the American Association for Cancer Research 100th Annual Meeting 2009.