U.N. Agency Links the Pill, Hormones to Cancer
Overall Risk Unclear as the Pill Also Lowers Risk of Some Cancers
July 29, 2005 -- Researchers from a U.N. cancer agency are calling combined estrogen-progestin birth control pills and menopausal hormone replacement "carcinogenic to humans."
However, they don't dismiss either type of drug. For instance, they state that birth control pills may "slightly" raise the risk of some cancers while lowering risks of other cancers.
Women should weigh the drugs' risks and benefits with their doctors, write the researchers.
The report appears in The Lancet Oncology. The researchers included Vincent Cogliano, PhD, of the World Health Organization's International Agency for Research on Cancer (IARC).
They didn't do any new studies. Instead, they reviewed past research on the topic.
The risks are not new and are already noted on drug labels, says Candace Steele, director of global public relations for Wyeth Pharmaceuticals, which makes birth control pills and menopausal hormone therapy drugs.
Review of Birth Control Pill Studies
The researchers write that combined estrogen-progestin birth control pills may "slightly" raise breast cancer risk in women currently or recently taking those pills. But the risk seems to drop back to normal 10 years after stopping the pill, write the researchers.
The researchers note higher risks of cervical and liver cancers with combined birth control pills.
However, uterine and ovarian cancer risk is lower in women using birth control pills, they write.
Despite the slightly higher risk of some cancers, the overall risk of cancer from the pill is still low.
The IARC's assessment of cancer risk from birth control pills hasn't changed but now includes more types of cancer, write the researchers.
Because use of the pill (forms containing both estrogen and progestin) heightens risk of some cancers and reduces that of others, it is possible that there may be an overall net benefit to public health, write the researchers. More rigorous analysis is needed to show this, they add.
The researchers cite studies showing higher breast cancer risks for women using combined hormone therapy -- containing both estrogen and progestin. They note other studies showing that uterine cancer risk is higher in women taking estrogen-only therapy, compared to those taking estrogen and progestin.