Birth control pill may cause breast cancer

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Birth control pills may increase breast cancer risk

- Birth control pills containing high doses of
oestrogen, 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 Centre
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 found.

Oestrogen linked to cancer risk
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 familyhistory.

In addition, they found that the link was slightly
stronger – though not statistically significant – for
breast cancers termed oestrogen-receptor positive. This
type of cancer needs oestrogen to grow, which might
help explain why high-dose oestrogen pills elevated
risk.
The researchers also found variations in risk among
different formulas, with low-dose oestrogen pills
appearing safest. "Recent use of oral contraceptives
containing low-dose oestrogen [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.
High-dose oestrogen 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
to Beaber.
Pills with ethynodiol diacetate – a progestin – appeared
to increase the risk of breast 2.6 fold, Beaber said.
Risks seemed lower with moderate-dose oestrogen 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 cancer.
Electronic pharmacy records
"The specific doses and types of hormones used in oral
contraceptives are included in packaging information,"
Beaber said.
The study, funded by the National Cancer Institute, was
published on 1 August in the journal Cancer Research.
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
oestrogen 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, California.
Other factors
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
oestrogen birth control pill that does not contain the
higher-risk progesterone," Vito said.
"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 control pills.