The more you smoke, the higher your risk of one type of skin cancer, report scientists from the Netherlands.
In a study of nearly 1,000 people, those who smoked were 3.3 times more likely to get squamous cell carcinoma than those who did not smoke, the study reports. The researchers found no connection between smoking and the other two main types of skin cancer -- basal cell and melanoma.
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"We expected an association for this type of skin cancer, but it was a little bit higher than we thought it would be," says researcher Dr. Marshall Bastiaens, of Leiden University Medical Center in the Netherlands.
Squamous cell carcinoma is responsible for about 20 percent of all skin cancers. Like other skin cancers, it most often occurs in sun-exposed areas of the body -- the head, neck, arms and the backs of hands -- but can be aggressive, invading tissues beneath the skin. However, unless it spreads to the lymph nodes, which happens rarely, the five-year survival rate for the disease is 95 percent.
Reason unknown
Bastiaens can't say why smoking seems to be associated with only squamous cell carcinoma.
"There are ideological factors that differ between the types of skin cancer," he says. Squamous cells seem to be affected more by sun exposure than basal cells, he says, and moles are associated with melanomas. "But we do not really know why [smoking] causes this type of skin cancer."
Still, the researchers found a clear connection between how much people smoke and their risk for getting the disease, Bastiaens says. Those who smoke one to 10 cigarettes a day are 2.4 times more likely to get squamous cell carcinoma than nonsmokers, the study says. For people who smoke 11 to 20 cigarettes a day, the risk triples, the study says, and for heavy smokers -- those who smoke more than 21 cigarettes a day -- it goes up to 4.1 times.
Bad news for ex-smokers too
Even former smokers are 1.9 times more likely to develop this type of skin cancer than people who've never smoked, the researchers say. Results of the analysis -- which included 580 people with skin cancer and 386 people without the disease -- appear in the January issue of the Journal of Clinical Oncology.
Although they don't know exactly how smoking affects the cells to increase the likelihood of skin cancer, Bastiaens speculates that smoking could damage the DNA in skin tissue.
"The carcinogens in cigarettes and tobacco could interact with the DNA and change the DNA in the cells," he says.
Dr. Ronald Shelton, a dermatologist at New York City's Mt. Sinai Hospital, suggests other possible reasons for the connection between smoking and skin cancer.
"I don't think it's a surprise that smoking is a toxin," Shelton says. Tobacco inhibits the amount of oxygen delivered to the cells of the body, he says, and that affects the health of the skin. "It can cause aging effects because of anti-oxygenation," he says.
"We [also] wonder if there is a systemic affect from the smoking that weakens the immune system," Shelton says.
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