Thursday, November 07, 2002
London -- Mammograms may increase the risk of breast cancer in women
genetically pre-disposed to the disease, a controversial German study
By Deirdre Lee
Radiobiologists at the University of Göttingen say their research
suggests that the low energy X-rays used in mammograms are nearly
three times as effective at mutating genes in human cells as
A typical 4-milligray mammogram could damage the genes in 16 out of
every 100 million cells, says researcher Dr Marlis
For women with inherited mutations in the BRCA1 or BRCA2 genes - which
greatly increase a woman's risk of breast cancer - mammograms could
therefore further increase their risk of disease, the team report in
New Scientist magazine.
Most women have two healthy copies of each BRCA gene, so the chances
of both being knocked out in the same cell are remote. But for women
with inherited mutations who have only one healthy copy of a BRCA
gene, the chances are much greater, researchers explain.
As many as 1 in 200 women have these genetic mutations, and they are
encouraged to have annual mammogram check-ups from as early as 25.
"It's a big risk for these women," says Dr Frankenberg-Schwager.
Researchers also reject the assertion by the UK National Radiological
Protection Board that there is no need to reconsider mammography
screening. The board's Roger Cox points to the International
Commission on Radiological Protection, in Stockholm, which estimated
that the additional risk from mammograms to women with BRCA mutations
was just a fraction of 1 per cent.
Researcher Dieter Frankenberg says this only applies to women over 40
and ignores the greater mutational effect of low-energy X-rays. His
calculations, which include evidence from the victims of Hiroshima and
Nagasaki as well as the findings on mammogram X-rays, conclude that
any women under 20 who have 10 mammograms of 4 milligrays increase
their chance of breast cancer by a factor of 2.5.
Although there are no figures for women under 20 with BRCA mutation or
those aged between 20 and 40, the team believe the risk is far greater
than a fraction of a per cent.
Dr Frankenberg-Schwager says that women with genetic mutations should
avoid frequent and early mammograms, and instead insist on other
methods of screening such as magnetic resonance imaging, which has
recently been found to distinguish between benign and cancerous breast
Bernie Gardner, information nurse at the UK's Breast Cancer Care,
says, "Although the findings of this research are interesting and
should be followed by further work, mammography is still a valuable
tool in the detection of early breast cancer."