Toenail clippings may predict lung cancer
Study shows nicotine levels in toenails may indicate lung cancer risk
7th March 2011 -- Toenail tests tell whether you're at high risk of getting lung cancer from cigarette smoke, even if you're not a smoker.
The finding comes from the toenails of 210 men with lung cancer and a comparison group of 630 men without lung cancer who joined a US study called the Health Professionals Follow-Up Study. Most of the 33,737 medical professionals in this long-term study donated toenail clippings in 1987.
The 20% of toenails containing the highest amounts of nicotine identified men at the highest risk of lung cancer. These men were 10.5 times more likely to have lung cancer than the 20% of men with the least nicotine in their toenails.
Even when taking into account reported smoking -- that is, when comparing men at similar levels of cigarette use -- men with the most nicotine in their toenails were still over 3.5 times more likely to get lung cancer than those with the least toenail nicotine.
"Regardless of whether you are a smoker or a nonsmoker exposed to secondhand tobacco smoke, we can now better measure your exposure and predict your risk," study researcher Dr Wael K. Al-Delaimy tells us. Al-Delaimy is chief of the division of global health at the University of California.
Al-Delaimy was looking for a way to evaluate secondhand smoke exposure. He first measured nicotine in hair. But while working at Harvard with study co-author Dr Walter Willett, he learned that Willett and colleagues had collected a large number of toenail samples from medical professionals.
"Given that hair and toenails are formed of the same kind of tissue, I thought maybe we could analyse toenails for nicotine," he says. "Toenails can be stored at room temperature for years. And they represent nicotine exposure during the past year."
In fact, Al-Delaimy and colleagues have shown that toenail nicotine levels are closely linked to smoking status six years prior to collection of clipping samples. They have also shown that toenail nicotine levels predict the risk of heart disease in women. Women with the highest toenail nicotine levels have a 42% higher risk of heart disease than do those with the lowest levels.
Tobacco's true risk
"We knew tobacco was harmful, but we are now learning it is even more harmful than we had previously measured," Al-Delaimy says. "We are getting a better estimate of the true risk of tobacco's lung effects and this could be applied to other disease outcomes such as coronary heart disease, too."
Al-Delaimy and Willett report their findings in the American Journal of Epidemiology, published online ahead of the print edition.
In an emailed statement, Ed Yong, Cancer Research UK’s head of health evidence and information, says: “While toenails are unlikely to form the basis of a screening test, these results show that chemicals in tobacco smoke can affect many other parts of the body beyond the mouth and lungs. Tobacco can cause cancers in many organs such as the kidney, pancreas, liver, stomach, bladder and cervix.”