Birth Control Pill Linked to Cervical Cancer

Risk of disease related to length of use

THURSDAY, April 3, 2003 (HealthDayNews) -- Women who use birth control pills have an increased risk of cervical cancer the longer they are on the contraceptive, a British study confirms.

The study was done to give more definite information about the risk, which previous research has established. The U.S. Food and Drug Administration recently revised contraceptive labels to include that risk. What the new study provides, says Debbie Faslow, director of breast and gynecological cancer for the American Cancer Society, is more detail on the relationship.

The risk is directly related to length of time women use hormonal contraceptives, as they are formally known, says a report in the April 5 issue of The Lancet. And while the risk is higher for women infected with the human papillomavirus (HPV), which is thought to be the major cause of cervical cancer, using the pill elevates the risk for women free of HPV, the researchers say.

That relationship holds when many other possible risk factors are taken into account, including number of sexual partners, use of cigarettes, and whether or not a woman has screening for cervical cancer, says Dr. Amy Berrington, a research fellow at the Cancer Research United Kingdom Epidemiology Unit, a lead author of the report.

"We have done everything we could with these data to be sure that there are not confounding factors," says Berrington.

Working with the French International Agency for Research on Cancer, the British epidemiologists reviewed data from 28 studies that included more than 12,500 women with cervical cancer. They found that the risk was increased 10 percent in a woman who used the pill for less than five years (compared to women who never used it), 60 percent for someone who used it for five to nine years, and was doubled for 10 years use or more.

The study doesn't establish a cause-and-effect relationship, Berrington says. "I don't think we can ever say that with certainty," she says. And Faslow says something else must be involved, because cervical cancer has nothing to do with hormones of the kind used in the pill.

She suspects it might have something to do with decreased use of condoms, which help prevent HPV infection, although the British study found that the use of such barrier contraceptives did not affect the result.

A problem with an epidemiological study is that it can rely on a person's memory of past behavior, says Dr. Carol L. Brown, assistant attending surgeon at Memorial Sloan-Kettering Cancer Center in New York. "No matter how well the study is planned, there are potential biases," she says. The results might be affected by such personal factors as the kind of woman who takes oral contraceptives or the frequency of intercourse, Brown says.

So while this meta-analysis of many studies suggests that there may be an association, there is no absolute proof.

Worldwide, cervical cancer is the second leading cancer in women, but most of those cases occur in underdeveloped countries. In the United States, there are 12,000 cases and 4,000 deaths a year, Faslow says.

A big question now is how long the increased risk lingers after a woman stops using the pill. An international study has been set up to try to determine that, Berrington says.

More information

To learn more about cervical cancer, consult the National Institutes of Health or the American Cancer Society.

SOURCES: Amy Berrington, M.D., research fellow, Cancer Research United Kingdom and University of Oxford, Oxford, England; Debbie Faslow, Ph.D., director of breast and gynecological cancer, American Cancer Society, Atlanta; Carol L. Brown, M.D., assistant attending surgeon, Memorial Sloan-Kettering Cancer Center, New York; April 5, 2003, The Lancet
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