HealthyCanada.com

2003/4/10

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.

According to the results of the study 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 12500 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) and 60 percent for someone who used it for five to nine years.

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.

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.

Worldwide cervical cancer is the second leading cancer in women but most of those cases occur in underdeveloped countries.

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.