1. Every
year millions of women are screened with X-rays to pick up signs of breast
cancer. If this happens early enough, the disease can often be treated
successfully. According to a survey published last year, 21 countries have
screening programmes. Nine of them, including Australia, Canada, the US and
Spain, screen women under 50. 2. But the medical benefit of
screening these younger women are controversial, partly because the radiation
brings a small risk of inducing cancer. Also, younger women must be given higher
doses of X-rays because their breast tissue is denser. 3.
Researchers at the Polytechnic University of Valencia analysed the effect of
screening more than 160,000 women at 11 local clinics. After estimating the
women's cumulative dose of radiation, they used two models to calculate the
number of extra cancers this would cause. 4. The mathematical
model recommended by Britain's National Radiological Protection Board (NRPB)
predicted that the screening programme would cause 36 cancers per 100,000 women,
18 of them fatal. The model preferred by the UN Scientific Committee on the
Effects of Atomic Radiation led to a lower figure of 20 cancers.
5. The researchers argue that the level of radiation-induced cancers is
"not very significant" compared to the far larger number of cancers that are
discovered and treated. The Valencia programme, they say, detects between 300
and 450 cases of breast cancer in every 100,000 women screened.
6. But they point out that the risk of women contracting cancer from radiation
could be reduced by between 40 and 80 percent if screening began at 50 instead
of 45, because they would be exposed to less radiation. The results of their
study, they suggest, could help "optimize the technique" for breast cancer
screening. 7. "There is a trade-off between the diagnostic
benefits of breast screening and its risks," admits Michael Clark of the NRPB.
But he warns that the study should be interpreted with caution. "On the basis of
the current data, for every 10 cancers successfully detected and prevented there
is a risk of causing one later in life. That's why radiation exposure should be
minimised in any screening programme." A．Harm Screening May Do
to a Younger Woman B．Investigating the Effect of
Screening C．Effects Predicted by Two Different Models
D．Small Risk of Inducing Cancers from Radiation
E．Treatment of Cancers F．Factors That Trigger Cancers
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A．be costly
B．harmful
C．save a life
D．still open to debate
E．reduce the risk of radiation triggering a cancer
F．reduced to the minimum
Early discovery of breast cancer may ______.
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Advantages of screening women under 50 are ______.
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Delaying the age at which screening starts may ______.