Screening of smokers urine for NNAL & cotinine can predict lung cancer risk

Higher levels of NNAL & cotinine –byproducts of tobacco smoke –raise chances of developing lung cancer by several-fold.

Higher levels of two chemical substances – NNAL and cotinine –which form as the byproducts of the tobacco smoke thrown out of the body through urine can say the risk of developing lung cancer in smokers, according to a  new study where researchers in Minnesota, Singapore and China examined findings from two prior surveys..  

NNAL and cotinine levels in the urine were linked to lung-cancer rates as much as 8.5 times higher than those of other smokers, said Jian-Min Yuan, the study leader and an associate professor of public health at the University of Minnesota in Minneapolis.

“If we can identify a smoker with a high level of metabolites, and down the road they have a higher risk of lung cancer, public health workers can get them motivated to quit smoking,” Yuan said. “If they can’t quit, we can do more intensive screening to find very small lung cancers that can be treated.”

The team of researchers analyzed varying levels of metabolites in the urine of about 500 smokers drawn from the Shanghai Cohort Study and the Singapore Chinese Health Study, funded by the U.S. National Cancer Institute in Bethesda, Maryland.

Dividing smokers into those having high, medium and low levels of the two chemicals, the researchers followed lung cancer diagnoses for 10 years.

One study looked at more than 18,000 men who enrolled when they were aged 45-64 in Shanghai, China. The other study included more than 63,000 men and women of Chinese descent, aged 45-74, and was conducted in Singapore between 1993 and 1999.

The researchers found that the third of smokers who had the highest levels of NNAL and a marker called cotinine were 8.5 times more likely to develop lung cancer than those with levels in the lowest third and similar histories of smoking.

NNAL  –4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL)– is a known carcinogen –a substace capable of inducing cancer in lab animals. If the Smoker’s NNAL levels had twice the risk of getting lung cancer compared with smokers who had low levels.

Whereas high urine levels of cotinine, a nicotine byproduct, had three times the risk of those with low levels. Smokers with high levels of both NNAL and cotinine were 8.5 times more likely to get lung cancer than comparable smokers who had low levels of both chemicals.

Both NNAL and cotinine appeared to be independent risk factors for lung cancer, even after adjusting for daily pack usage and the number of years of smoking reported by study participants, Yuan said.

Currently, there is no way to determine which smokers are most likely to develop lung cancer. Doctors do know that smokers with chronic obstructive pulmonary disease or a prior family history of lung cancer are at higher risk.

However, the new urine test may take three to five years to validate the test in ethnic groups around the world, refine the technology, and add other chemical carcinogens such as polycyclic aromatic hydrocarbons to the test panel, the researches said.

Scientists could perfect the predictive powers of the test, which costs about $100 to $120, within a few years, Yuan said.

What are the chemicals in tobacco?

Cigarettes, cigars, and smokeless and pipe tobacco consist of dried tobacco leaves, as well as ingredients added for flavor and other properties. More than 4,000 individual compounds have been identified in tobacco and tobacco smoke. There are about 60 possible carcinogens –cancer causing –in tobacco smoke.

There are hundreds of substances added by manufacturers to cigarettes to enhance the flavor or to make the smoking experience more pleasant. Some of the compounds found in tobacco smoke include ammonia, tar, and carbon monoxide.

Nicotine is the addictive drug in tobacco. Regular use of tobacco products leads to addiction in a high proportion of users.

Nicotine is found in substantial amounts in all forms of tobacco. It is absorbed readily from tobacco smoke in the lungs and from smokeless tobacco in the mouth or nose and rapidly spreads throughout the body.

Lung cancer: The most lethal

Lung tumors are the most lethal form of cancer in the U.S., spurring 161,840 deaths and 215,020 new cases in 2008, according to the American Cancer Society, based in Atlanta.

The U.S. Centers for Disease Control and Prevention estimates that about 23 percent of adult Americans are smokers, and smokers account for about 87 percent of cases of lung cancer, the number one cancer killer.

According to the Centers for Disease Control and Prevention (CDC), 46.2 million US adults were current smokers in 2001 (the most recent year for which numbers are available). This is 22.8% of all adults (25.2% of men, 20.7% of women) – nearly 1 in every 4 people.

When broken down by race/ethnicity, the numbers were as follows:

Whites – 24.0%

African Americans – 22.3%

Hispanics – 16.7%

American Indians/Alaska Natives – 32.7%

Asian Americans – 12.4%

The numbers were higher in younger age groups. Almost 27% of those 18 to 24 years old were current smokers. Nationwide, 22.9% of high school students were current smokers in 2002. White and Hispanic students were among the highest in terms of cigarette use.

Each year, 440,000 people die in the US alone from tobacco use.

Cigarette smoking accounts for at least 30% of all cancer deaths. It is a major cause of cancers of the lung, larynx (voice box), oral cavity, pharynx (throat), and esophagus, and is a contributing cause in the development of cancers of the bladder, pancreas, liver, uterine cervix, kidney, stomach, colon and rectum, and some leukemias.

About 87% of lung cancer deaths are caused by smoking. Lung cancer is the leading cause of cancer death among both men and women, and is one of the most difficult cancers to treat. It is very hard to detect when it is in the earliest, most treatable stage.

Smoking is also a major cause of heart disease, bronchitis, emphysema, and stroke, and contributes to the severity of pneumonia. Tobacco has a damaging affect on women’s reproductive health and is associated with increased risk of miscarriage, early delivery (prematurity), stillbirth, infant death, and is a cause of low birth weight in infants.

The CDC estimated that adult male smokers lost an average of 13.2 years of life and female smokers lost 14.5 years of life because of smoking. Although 70% of smokers want to quit and 35% attempt to quit each year, less than 5% succeed. The low rate of successful quitting and the high rate of relapse are related to the effect of nicotine addiction.

People who stop smoking at younger ages experience the greatest health benefits from quitting. Those who quit by age 35 avoid 90% of the risk due to tobacco use. However, even smokers who quit after age 50 substantially reduce their risk of dying early.