Quelle:
Presse-Information Fachblatt The Lancet
Pille schützt viele Jahrzehnte lang vor Eierstockkrebs
Die Einnahme der Antibabypille kann jährlich zehntausende von
Leben retten. Frauen die in der Vergangenheit die Pille verordnet
bekamen, haben ein deutlich geringeres Risiko an Eierstockkrebs
zu erkranken. Wissenschaftler fordern daher "Weg mit
der Rezeptpflicht!", da diese unnötigerweise den Zugang zu
einem wichtigen Anti-Krebsmittel erschwert.
Im
renommierten Fachblatt The Lancet wurde kürzlich ein Artikel
publiziert (siehe unten), der aufgrund seiner beeindruckenden
Daten die Frage endgültig beantwortet, ob die Mehrzahl der Frauen
ein orales Kontrazeptivum - gemeinhin als "Antibabypille"
bekannt - einnehmen sollten oder lieber nicht.
Valerie Beral und ihre Kolleginnen und Kollegen analysierten 45
epidemiologische Studien, die in den vergangenen Jahren den Zusammenhang
zwischen der Einnahme der Pille und dem Auftreten des in den meisten
Fällen tödlich verlaufenden Eierstock-Krebses (Ovarial Karzinom)
untersuchten. An den Studien nahmen 7.308 Frauen mit und
32.717 Patienten ohne Eierstockkrebs teil, die alle irgendwann
in ihrem Leben die Antibabypille eingenommen hatten.
Diese
sog. Metaanalyse aller vorhandenen Untersuchungen zeigt ohne jeden
Zweifel, dass die Einnahme einer beliebigen Antibabypille auch
noch viele Jahre später in der Lage ist, das Risiko an Eierstockkrebs
zu erkranken deutlich vermindert.
Diese positive Wirkung der Pille beginnt sehr schnell und
nimmt bei einer Langzeiteinnahme weiter zu. Die Autoren kamen
zu dem Schluss dass die oralen Kontrazeptiva in den vergangenen
50 Jahren weltweit mindestens 200.000 Fälle von Eierstockkrebs
und 100.000 entsprechende Todesfälle verhindert haben.
Doch
die Erfolgsstory der Pille wird täglich neu geschrieben. Alle
zusammengetragenen wissenschaftlichen Daten sprechen nach
Meinung der Experten dafür, dass durch die Einnahme
der Pille in Zukunft pro Jahr mindestens 30.000 Fälle von
Eierstockkrebs verhindert werden. Diese Funde - so die Autoren
der Studie - setzen einen völlig neuen Standard für die Möglichkeit
einen tödlichen Krebs durch Vorsorgemaßnahmen zu verhindern.
Eierstockkrebs
ist in den USA die häufigste Ursache für den Tod aufgrund eines
gynäkologischen Tumors. Da es keine praktikablen Früherkennungsmaßnahmen
gibt, wird der Eierstockkrebs meist in einem späten Stadium entdeckt
und kann dann nicht mehr geheilt werden.
In
einem die Untersuchung begleitenden Editorial wird mit Nachdruck
die Forderung aufgestellt, die Rezeptpflicht für die Pille abzuschaffen,
da diese eine unnötige Barriere darstellt, die viele Frauen davon
abhält, sich die Pille zu beschaffen.
Selbstverständlich
trifft es auch nach der Veröffentlichung dieser Studie weiter
zu, dass die Langzeiteinnahme der Pille bei einzelnen Frauen auch
negative Auswirkungen haben kann. Umstritten ist bisher beispielsweise,
ob die Pille das Risiko für Brust- und Gebärmutterhalskrebs möglicherweise
leicht erhöht. Und selbstverständlich sollten auch in Zukunft
jene Frauen die Pille nicht über einen längeren Zeitraum einnehmen,
bei denen die auf Risikofaktoren basierenden bekannten Kontraindikationen
vorliegen - wie beispielsweise Lebererkrankungen, oder eine familiäre
Häufung von Thrombosen.
Bilanziert
man aber die bewiesenen Vor- und denkbaren Nachteile der Langzeiteinnahme
der Antibabypille, so überwiegt aus wissenschaftlicher Sicht
der Nutzen den denkbaren Schaden bei weitem.


Den
Volltext des Artikels als PDF-Datei finden Sie hier
hier
Lancet
2008; 371: 303–14
The case for preventing ovarian cancer
In today’s Lancet, Valerie Beral and colleagues provide a definitive
analysis of the association between oralcontraceptives and ovarian
cancer. Although thefindings are not unexpected, this study is
impressiveand compelling. It pools worldwide data from 45 epidemiological
studies and shows beyond doubt that
ovarian cancers can be prevented by the long-termuse of different
generations of oral contraceptives.
Moreover, this substantial protection begins quickly, and
increases with increasing duration of use.In population
terms, the findings are dramatic.
The authors suggest that during the past 50 years,200 000 cases
of ovarian cancer and 100 000 deathsfrom the disease have already
been prevented worldwidethrough the use of oral contraceptives.
They
calculate that at the current level of contraceptive use, at
least 30 000 cases of ovarian cancer could eventually be
prevented every year. These findings set a new standard
in primary prevention for a deadly cancer and haveimportant public-health
implications.
Ovarian cancer is an aggressive and fatal disease. Inthe USA,
ovarian cancer is the most common cause ofdeath from a gynaecological
malignancy. Older womenare at highest risk; around two-thirds
of affected womenare 55 years or older. The absence of proven
screeningmethods and specific symptoms means that ovariancancer
is often diagnosed late.
Despite
advances in treatment, long-term survival rates remain poor—thus
primary prevention would be a major advance.This latest study
raises the question again of whetheroral contraceptives should
be made more widelyavailable to women to protect them from ovariancancer.
We believe that the case is now convincing.
Women deserve the choice to obtain oral
contraceptives
over-the-counter, removing a huge and unnecessarybarrier
to a potentially powerful cancer-preventingagent. Since the introduction
of oral contraceptivesin the 1960s, there have been many
debates abouttheir health benefits and safety. In the current
eraof the combination pill with low-dose oestrogenformulations,
the adverse cardiovascular effects areshort
term and have diminshed over time. The effectof oral
contraceptives on cancer risk is more complex.
Whilst being shown to decrease the risk of ovarian and endometrial
cancers, oral contraceptives may increase
the risk of breast and cervical cancers. However, the
best evidence on the net effect of oral contraceptives shows a
reduction in risk of cancers. Given the well established benefits
of avoiding pregnancy, which has a high morbidity and some mortality,
even in developed countries, the risk-benefit equation is
weighted strongly in favour of giving oral
contraceptives to women who seek them, and who are not contraindicated
from taking them.
Oral contraceptives have become the keystone of reproductive health
by virtue of their ability to prevent pregnancy. But whether women
in their 20s will be prepared to take an oral contraceptive
to prevent ovarian cancer where the life-time risk is low (1
in 70) remains open to uncertainty. While the average 20-year-old
woman may not be thinking about whether she will get ovarian cancer
(she is more likely to be concerned about breast and cervicalcancer,
where the lifetime risk is much higher), a strong message about
the overall cancer preventing benefits of oral contraceptives
would be a positive public-health message, empowering women to
decide
for themselves about the evidence. Women contend with much adverse
publicity about the risks of oral contraceptives, which surely
influences their decision about whether to take these agents.
Very little is said in the press about the health benefits.
Today’s
paper in The Lancet helps to redress that balance.There are few
drugs available that confer powerful and long-lasting protection
against a highly lethal malignancy after such a short exposure.
In translating the evidence from this large systematic review
to individual women, oral contraceptives
should now be made more widely available. Contraindications
include a history of thromboembolism, heart disease, migraine,liver
disease, and several other relatively uncommon conditions. The
benefits of oral contraceptives in primary ovarian cancer are
independent of the preparation,and vary little by ethnic origin,
parity, family history of
breast cancer, body-mass index, and use of hormone replacement
therapy.
We strongly endorse more widespread over-the counter access to
a preventive agent that can not only prevent cancers but also
demonstrably save the lives of tens of thousands of women.
For more on the net effect of
oral contraceptives see
BMJ 2007; 335: 651
For
more on health benefits and
safety of oral contraceptives
see Am J Obs Gynae
Correspondence to:
Secretariat, Cancer
Research UK
Epidemiology Unit,
Richard Doll
Building, Roosevelt
Drive, Oxford
OX3 7LF, UK
collaborations@ceu.ox.ac.uk
Ovarian cancer
and oral contraceptives
Since the 1960s, oral contraceptives have become a dominant form
of female contraception in most developed countries. In the UK,
25% of women aged 16–49 years and 62% of women aged 16–24 years
rely on combined oestrogen–progestin or progestin-only
(minipill) oral contraceptives.1
In the USA, 19%
of women aged 15–44 years (and 32% of 20–24-year-olds) take oral
contraceptives. 2 These drugs are the most effective reversible
birth-control method, and widespread use has been the cornerstone
of family-planning initiatives worldwide. A causal role for oral
contraceptives invarious cancers was first suspected soon after
their use became widespread, but today’s low-dose formulation
are relatively safe drugs. Oral contraceptives have been linked
with increased risks for some cancers (breast andcervix) and with
protective effects for others (ovarian, endometrial, and colorectal).3
Calculation of
the net effecton women’s health is fraught with uncertainties.
There are inherent difficulties associated with ascertaining the
nature of exposure to oral contraceptives, such as age at first
use, duration of use, time since last use, formulation of contraceptives
(sequential, combined, orprogestin-only), and dose. Furthermore,
epidemiological studies must include information about potential
confounders, such as sociodemographics, family history of cancer,
comorbidity, reproductive-health variables, history of hormone-replacement
therapy (HRT), and relevant lifestyle characteristics.
For a woman in her 50s or 60s, recalling past use of oral contraceptives
is not easy.
In case-control
studies, recall bias may further compoundthis problem because
women with cancer might make a greater effort to recollect past
exposures than their cancer-free counterparts.Recall bias might
be the most relevant confounderin the recent studies in populations
with substantial media exposure to the knowledge that drugs such
as oral contraceptives can have harmful effects.
Prospective cohort
studies are mostly free of recall biases because
exposure information is collected before the onset of the cancer
outcome. However, prospective cohorts are more expensive and tend
to have lower statistical power than case–control studies. Except
for cervical cancer, for which increases in risk are more than
moderate,4 directions of changes in risks associted with ever
having used oral contraceptives are variable and modest, in the
range of 10–50%, for ovarian, endometrial, breast, and colorectal
cancers.3 Precise and accurate measurementof
modest relative risks and disentangling them from spurious confounders
require very large studies. Individually,each study has little
or no hope of furthering our understanding of how risk varies
by histological subtype, menopausal status, or other relevant
variables for which the assessment of stratum-specific associations
would provide useful insights into causation.
For these reasons and more, the study by the Collaborative Group
on Epidemiological Studies of Ovarian Cancer5 in today’s Lancet
makes a major contribution to our understanding of the role of
oral
contraceptives in the causation or prevention of ovarian cancer.
The researchers
took advantage of the great statistical precision afforded by
the combination of 45 studies, many of which were prospective
cohorts. The Collaborative Group tackled many questions about
the quantitative effects of oral contraceptive use, age at start,
duration of use, time since cessation, and era of use, all infinely
stratified analyses that accounted for key a-priori
confounders and design variables. The Group calculates that use
of oral contraceptives will eventually prevent 30 000 ovarian
cancers per year. The notion that this unequivocal protective
effect stems from the cumulative suppression of ovulatory cycles
was strongly supported by the homogeneity of results across eras
of use (as
a proxy for oestrogen dose) and in the long-lasting protective
effect after cessation of use. Reassuringly, case–control
studies reproduced, on average, the same magnitude of protective
effect found in cohort studies, which assuages concerns about
recall bias.
The Collaborative Group’s new analysis provides useful insights
into the association with ovarian-cancer histology. The protective
effect was largely the same for epithelial and non-epithelial
tumours, although there was less evidence that oral contraceptive
use prevents mucinous ovarian cancer, which accounts for fewer
than 15% of all incident cases .
Oral contraceptives
are not the only exogenous source hormones that might influence
ovarian cancer risk in women. The Million-Women Study by the same
group6 found that the mucinous ovarian cancer differed from
other types after HRT. Use of HRT was associated with increased
risk of serous and mixed histology
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