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Women from 50 years of age should participate
in breast screening. This should be within programmes with
quality control procedures in compliance with European Union
Guidelines for Quality Assurance in Mammography Screening.
Mammography can detect breast tumours
at a clinically undetectable
stage. The results of the early randomised trials of mammographic
screening demonstrated the value of this technique and
led to the introduction of organised national programmes of
screening in several countries in 1986–8. Reports from
seven
trials involving over half a million women subsequently indicated
a reduction in mortality from breast cancer of about 25% in
women
invited to be screened. The reduction of mortality in those
actually
attending screening is about one third.
There
is now considerable evidence that breast cancer screening
with mammography is effective in reducing mortality from breast
cancer. An overview of the Swedish trials reported relative
risks of death of 0.71 in the group randomised to receive
an offer of screening, with 95% confidence internal 0.57–0.89
for women aged 50–59 years at entry. Results for women
ages 60–69 were almost identical. When applied to a
population, a well-organised programme with a good compliance
should lead to a reduction in breast cancer mortality of at
least 20% in women aged over 50.
The
value of screening women aged under 50 years is uncertain.
No
trials have had large enough statistical power to analyse
these
women separately. What recommendations should be made for
mammographic screening of women aged between 40 and 49 is
an
important question that cannot currently be answered; over
40%
of the years of life lost due to breast cancer diagnosed before
the
age of 80 years are attributable to cases presenting symptomatically
at ages 35–49 years, frequently an age of considerable
social responsibility.
Swedish
workers have recently conducted an overview of four
of their trials. The conclusions indicate that the benefit
of breast
screening, in terms of a reduction in breast cancer mortality
of
21%, persisted for a median time of 15.8 years. In addition
to this
overview, two working groups have been convened. A working
group of the
International Agency for Cancer Research (IARC)
met in Lyon on 5–12 March 2002 and consisted
of 24 experts from 11 countries. The quality of the seven
trials was assessed and it was concluded that screening by
mammography reduced mortality from breast cancer in women
of 50–69 years of age. In women who participated in
screening
programmes this reduction was estimated at 35%. For women
of
40–49 years, evidence for a reduction in mortality was
too limited
to reach a conclusion. The evidence is insufficient to recommend
performing routine breast self-examination as a method of
screening.
Forty
years of clinical trials, the contribution of hundreds of
scientists and health workers and the dedication of hundreds
of thousands of women to participate in studies lasting for
decades has resulted in adequate evidence to support the efficacy
of mammographic screening for breast cancer, which now allows
its transfer to the arena of public health care . Doctors
and women should be assured that participation in organised
screening programmes with high quality control standards is
of benefit, provided appropriate investigation and treatment
is available. European Guidelines for Quality Control in Mammographic
Screening have been developed and are widely employed throughout
Europe.
Special
efforts should be made to encourage screening among the more
deprived members of communities. It is important not to over-emphasise
the benefit of screening, and to appreciate that mammographic
screening is but one step in the total care of women with
the disease. As had been shown by long-term established programmes
in the UK, Sweden, Finland and The Netherlands recognition
of the importance of the multidisciplinary team in the assessment
of mammographic abnormalities spread into the symptomatic
sector leading to the development of integrated multidisciplinary
breast care centres. Staffed by dedicated surgeons, radiologists
and pathologists working alongside breast care nurses, counselling
and other support personnel, these centres offer the necessary
care for women with breast cancer.
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