U.N. Agency Links the Pill, Hormones to Cancer
Overall Risk Unclear as the Pill Also Lowers Risk of Some Cancers
WebMD News Archive
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 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
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.
When progestin is taken every day, the risk is much the same as that in
women who have never used hormonal treatment, they write.
"There are both beneficial and adverse effects for oral contraceptives
and menopausal therapy," states an IARC news release. Each woman who uses
these products should discuss the overall risks and benefits with her
Drug Company: Nothing New Here
The IARC's change regarding combined hormone therapy "is based on data
published since 1999," Steele tells WebMD.
"Estrogen and progestin data from those studies have previously been
published in medical literature and have been incorporated into the product
labeling for estrogen and progestin therapies," she says.
"I think it's important to note that the information in the IARC's most
recent guidelines is consistent with the current clinical practice and all
class labeling for our company's estrogen and estrogen-plus-progestin
therapies, as well as for our oral contraceptive products," says
"The IARC last made their report in 1999, so they're just updating [it]
based on new information since then. We, of course, have been updating our
label all along. So the information that's included in that report is already
included in our label," says Steele.
Millions of women use oral contraceptives or hormone therapies, notes
Steele. "I really feel that the best source of information is a woman's
physician, and that this information should be taken in context with a risk and
benefit assessment made with her physician," she says.