Women smokers with HPV multiply cancer risk

The combination causes risks to soar, research shows.
SCRIPPS HOWARD
Women who smoke and also carry high levels of the virus associated with cervical cancer are up to 27 times more likely to develop the most common form of cervical cancer compared with uninfected women who also smoke, results of a new study show.
The study by Swedish researchers involved data from Pap tests of more than 100,000 women, and identified 499 with cervical cancer that had not extended beyond the outer layer of tissue. They matched them with 499 other women who were similar in age and other characteristics, but cancer-free.
For those women, they compared smoking behavior with concentrations of human papilloma virus-16, the strain most associated with cervical cancer, and found that the combination caused risk to soar.
"Our study would imply a synergistic action between HPV and smoking that would greatly increase the likelihood of women developing cervical cancer if they are HPV-positive smokers," said Anthony Gunnell, a medical biostatistician at Karolinska Institute in Stockholm and lead author of the report published Friday in the journal Cancer Epidemiology, Biomarkers and Prevention.
Specific results
Women who smoked and had a high HPV load during their first exam had 27 times greater risk of later cancer than women who smoked but did not have an HPV infection.
Women who were positive for HPV (no matter how high their viral load) were 14 times more likely to develop cervical cancer than women who were HPV-negative and smoked.
Nonsmoking women with high HPV loads had just six times greater risk for cervical cancer compared to nonsmokers who were negative for the virus.
"Clearly, both exposures need to be present at the same time for there to be interaction," Gunnell said.
The study may also partly explain why some women may not get cervical cancer despite smoking or being HPV-positive, which are both known to contribute to the disease on their own.
Vaccine recommended
Government public health authorities in the United States have only recently begun recommending a vaccine against HPV for adolescent girls and young women in an effort to protect them from cervical cancer in the future.
Cervical cancer is one of the leading causes of cancer deaths worldwide, and death rates are particularly high in developing countries. In the United States, though the rate of incidence and mortality have fallen by 50 percent in the past 20 years, this year alone, of 9,700 diagnosed with cervical cancer, some 3,700 will die.
Gunnell and colleagues also found a relationship between how long a woman had smoked and cancer. "We found a statistically significant multiplicative interaction between duration of smoking and HPV presence during cervical cancer," he said.
This could be because smoking suppresses the immune system in such a way that HPV infection thrives, he said. Or it could be that both the virus and smoking suppresses levels of certain antibodies that control abnormal cell growth, thus encouraging cancer to spread.
"More likely it is a combination of both mechanisms that increases the risk," Gunnell said, adding that more research is needed to understand the interactions. In the meantime, health care providers should consider women smokers with heavy HPV infections at particular risk for cervical cancer, he said.