Some Birth Control Pills May Up Breast Cancer Risk08/01/14
THURSDAY, July 31, 2014 (HealthDay News) -- Birth control pills
containing high doses of estrogen, along with some other
formulations, may increase the risk of breast cancer in women under
50, new preliminary research suggests.
"There are numerous oral contraceptive formulations," explained lead researcher Elisabeth Beaber, a staff scientist at the Fred Hutchinson Cancer Research Center in Seattle. "Some of these formulations increase breast cancer risk while other formulations do not raise risk."
Overall, birth control pill use within the past year was
associated with a 50 percent increased risk of breast cancer risk
compared with former use or no use of birth control pills, Beaber
This study was designed to find a possible link between oral
contraceptive use and breast cancer risk in younger women. But, it
wasn't designed to prove that birth control pills definitively
cause the increased risk. However, the researchers did take into
account other factors that increase breast cancer risk, such as
family history. In addition, they found that the link was slightly
stronger -- though not statistically significant -- for breast
cancers termed estrogen-receptor positive. This type of cancer
needs estrogen to grow, which might help explain why high-dose
estrogen pills elevated risk.
The researchers also found variations in risk among different
formulas, with low-dose estrogen pills appearing safest. "Recent
use of oral contraceptives containing low-dose estrogen [20
micrograms ethinyl estradiol] did not appear to increase breast
cancer risk," Beaber said.
These lower-dose pills account for an increasing number of
prescriptions written today, Beaber said.
Which formulations seemed to raise the risk of breast cancer?
High-dose estrogen pills -- those containing 50 micrograms ethinyl
estradiol or 80 micrograms mestranol -- were associated with nearly
a three-fold higher risk of breast cancer, she said. Triphasic
combination pills with 0.75 milligrams of norethindrone were linked
to more than a three-fold higher risk of breast cancer, according
Pills with ethynodiol diacetate -- a progestin -- appeared to
increase the risk of breast 2.6 fold, Beaber said.
Risks seemed lower with moderate-dose estrogen pills -- those
with 30 to 35 micrograms of ethinyl estradiol or 50 micrograms
mestranol were linked to a 1.6 times higher risk of breast
How can a woman tell if she's taking a formulation linked to a
higher risk? "The specific doses and types of hormones used in oral
contraceptives are included in packaging information," Beaber
The study, funded by the National Cancer Institute, was
published Aug. 1 in the journal
Beaber stressed that the study results need to be confirmed
before any recommendations can be made to women. The results are
based on data about recent oral contraceptive use who were
diagnosed with breast cancer and nearly 22,000 healthy women who
served as the comparison group. The women were all between the ages
of 20 and 49.
The researchers used electronic pharmacy records to gather
information on prescriptions filled and information on formulas.
The study looked at the years 1990 through 2009.
The researchers evaluated the risks of breast cancer in women
who had taken birth control pills in the past year compared to
former or never users. They then looked at risk with the specific
formulas of birth control pills.
The study results suggest that the lower-dose estrogen pills,
which became popular in the 1990s, are not a problem, said Dr.
Courtney Vito, a breast surgeon and assistant clinical professor of
surgical oncology at the City of Hope Comprehensive Cancer Center
in Duarte, Ca.
While the researchers made a good attempt to answer the question
about risks associated with different birth control formulas, ''the
study has some flaws that are inherent in this type of study
design," Vito said. For instance, they could not control for all
factors that could increase breast cancer risk.
And, as the researchers also noted, the duration of time they
evaluated was relatively brief.
The best advice for women taking birth control pills? " Talk to
your doctor about considering a lower dose estrogen birth control
pill that does not have the higher-risk progesterone in it," Vito
"Although these results suggest an increased risk of breast cancer, the many established health benefits associated with oral contraceptive use... must also be considered when making individual choices," wrote the study's authors.
The study's authors also pointed out that any potential
increased risk likely goes down when a woman stops using birth
To learn more about risks for breast cancer, visit
American Cancer Society.
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