The Guardian
(UK), September 12, 2007
The
pill: new evidence shows it helps protect against cancer
40-year
study shows it cuts long-term risk of cancer of any kind by up
to 12%
By Sarah Boseley
The contraceptive
pill actually protects women against cancer in later life, according
to the largest study ever set up to evaluate the risks and benefits.
The pill, which
has been a source of controversy since it was introduced in the
1960s, is today revealed to have an overall net benefit for the
women who take it. Researchers who have followed 46,000 women
taking the pill - beginning in 1968 - say that it cuts the individual's
risk of cancer of any kind by up to 12%.
It is accepted
that the pill raises the risk of breast cancer while a woman is
taking it and for about five years afterwards. But the real benefits
kick in 15 years or more after she has stopped. Most women go
on the pill in their late teens or early twenties and have given
up by their late twenties, before the age when cancer becomes
most common.
The researchers,
who analysed 36 years of data from the Royal College of General
Practitioners' oral contraception study, show that women who were
once on the pill - as long as they did not take it for more than
eight years, and most do not - are no more likely to get breast
cancer than others.
And they are
significantly less likely to suffer from certain other cancers,
in particular ovarian cancer and endometrial cancer, which affects
the lining of the womb. They are also better protected from bowel
cancer. Women who took it for more than eight years had an increased
risk of cervical cancer.
Some effects
of the pill were already known, but this study, published online
today by the British Medical Journal, is the first to pull all
the cancer implications together.
Philip Hannaford
from Aberdeen University's department of general practice and
primary care, who headed the study, said: "Although there
have been some studies looking at groups of cancers, like all
the gynaecological cancers together, nobody has looked and said
what is the lifetime risk of any cancer if I take the pill and
how large is the risk." About 24% of women aged 16-49 are
currently on the pill, approximately 3.5 million.
Prof Hannaford
said he would not advise women to go on the pill specifically
to cut their cancer risk in later life.
"I would
never say that. I'm always conscious about the dangers of recommending
public health measures like that. It seems too simplistic to say
everyone should go on the pill. We have learned lessons. Five
to 10 years ago we might have said every menopausal woman should
go on HRT (hormone replacement therapy) to prevent heart disease.
Now we know that is very bad advice."
The pill and
HRT appear to have very different effects on health, even though
both are hormonal treatments. The latest findings from the Million
Women study, published recently in the Lancet, implicated HRT
in ovarian cancer deaths.
It was unclear
why the pill and HRT, used at different times in a woman's life,
should have such different impacts.
"I don't
think anyone can understand it at the moment, why there is a protective
effect before the menopause and a harmful effect afterwards,"
said Prof Hannaford.
The researchers
analysed data from about 65% of the 46,000 women who enrolled
in the study. Half those were taking the pill and half were not.
The data on their contraceptive use and health was collected from
their GPs and was not complete in every case.
Because of this,
the team did two sets of calculations: one using information only
from those women whose GPs were able to submit complete data,
and another using the data from all those originally enrolled,
together with notifications from the national cancer registries.
Using the first
dataset, they calculated that a woman's risk of developing any
cancer is cut by 3%, and using the bigger second dataset, they
put the reduction at 12%. If the true figure is 12%, there will
be one fewer cancer case for every 2,200 women using the pill,
they say, and if it is 3%, there will be one fewer for every 10,000.
The Family Planning
Association said the study confirmed that for most women, the
benefits of the pill far outweighed the risks. "Research
shows there may be a slight increased risk of developing cervical
cancer from oral contraception but more needs to be done to investigate
other factors such as sexual activity and smoking," said
Tony Belfield of the FPA.
"It is
important that health professionals have an open and informed
discussion with women and men so they can choose from the 14 different
contraceptive methods available to find the right one for them."
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