FRIDAY, Nov. 17, 2006 (HealthDay News) -- New research suggests that heavy smoking and high levels of a potentially deadly virus could combine forces and boost a woman's risk of developing precancerous lesions in the cervix.
Smoking and the human papillomavirus (HPV) have been linked to cervical cancer before. But the new study is the first to look at a possible interplay between heavy smoking and virus levels, said study author Anthony Gunnell, a researcher at the Karolinska Institutet in Stockholm, Sweden.
"The risk for developing pre-malignant cervical cancer increases as HPV load increases," Gunnell said. "Importantly though, it increases more with increasing HPV (levels) if you smoke than if you don't."
The American Cancer Society estimates that about 9,710 cases of cervical cancer will be diagnosed in the United States this year, and 3,700 will die.
However, the number of deaths dropped by 74 percent between 1955 and 1992, mostly because of the growing popularity of Pap tests that detect possible signs of cancer. Now, there is a vaccine available to prevent HPV infection and most cases of cervical cancer.
Scientists think a huge number of cervical cancer cases are caused by HPV, which may be the most common sexually transmitted disease. HPV seems to boost the risk of cancer by causing inflammation.
But how does it raise the risk, and why do some women get infected by HPV but never get cervical cancer?
In the new study, Gunnell and colleagues looked at the medical records of 738 women, including 375 with signs of precancerous cervical lesions and 363 healthy women. The researchers found the subjects by looking through a database of 146,104 women who underwent cervical screening in a region of Sweden between 1969 and 1995.
The findings are published in the November issue of Cancer Epidemiology, Biomarkers & Prevention.
The study authors wrote that there appears to be a "synergistic" relationship between heavy smoking and high levels of a specific strain of HPV.
Current smokers who had signs of HPV infection at the time of their first Pap smear were more than 14 times more likely to show signs of precancerous lesions than current smokers who weren't infected.
And heavy smokers who had high levels of HPV when first tested were 27 times more likely to have precancerous lesions. Among nonsmokers, however, high HPV levels only raised their risk by six times.
There's an important caveat: Since few American women develop cervical cancer now, a woman's chances of developing the disease still remain small.
It's not clear why smoking raises the risk of cervical cancer, but Gunnell said it may have something to do with how cigarette smoke affect the immune system. Both smoking and HPV affect molecules known as cytokines, which control tumor growth, he said.
What to do? Prevention is the first step, Gunnell said. "Women with HPV -- especially those with high HPV (levels) -- and who smoke are in a higher risk group. They should take particular care in being checked regularly. Obviously, it is to their benefit to also stop smoking."
Meanwhile, research will help scientists get a better handle on what causes cervical cancer, Gunnell said. "There are probably no immediate applications of this research regarding treatment per se. Of course, in science, every little bit counts, and you never know when a small bit of information can make a big difference to someone else's research."
More information
The American Cancer Society has more on risk factors for cervical cancer.
