A large local study here spanning more than a
decade has revealed some startling results: Asian women do not face the same
risk of getting breast cancer as women in the West.
Those
who have a close relative with this type of cancer are twice as likely to get
it, compared with a Westerner. But Asians with no such family history have only
half the risk.
So a
Singapore woman with a mother, sister or daughter with breast cancer is four
times more likely to get it too, compared with someone with no such family
history. This appears to be the case across the three major races here.
Previously,
based on the Western yardstick, those with family history were thought to have
double the risk.
This
has major implications on how doctors counsel their patients, said Dr Tan Min
Han, the senior researcher in the team. He is a researcher at the Agency for
Science, Technology and Research and a visiting consultant at the National
Cancer Centre Singapore (NCCS).
The
study suggested that women who had a lower risk of getting breast cancer 'would
benefit less from the use of mammography'.
On the
other hand, women with close relatives afflicted with breast cancer should talk
to their doctors and find out how they can reduce their risk of getting the
cancer, advised Dr Tan.
One
way, if they have got all the children they want, is to remove their ovaries,
as this cuts their risk. There is also medicine they can take to lower their
risk, he added.
More
than 1,550 women get breast cancer each year, and 370 die of it.
The
study results were published in the United States-based Breast Cancer Research
journal. It is the first such large-scale study done outside of Europe and
North America, and has implications for other Asian nations, the authors said.
The
NCCS study, started in 1994, tracked more than 28,000 women here aged between
50 and 64 for a decade.
Close
to 70,000 women were randomly selected, but only the 28,000 who had no cancer,
were not pregnant, and had not had a mammogram or biopsy done in the preceding
12 months were given a single, free mammogram. This was completed by February
1997.
The researchers
then checked against the cancer registry at five and 10 years after the
mammogram was done.
Cancer
reporting is compulsory in Singapore, and with the permission of the Health and
Home Affairs ministries, the researchers were able to check if any of the study
population had been diagnosed with breast cancer.
Based
on the Western model, 362 women from the study group should have contracted
invasive breast cancer after five years. But only 144 did. Similarly, 758 women
were expected to have the cancer after 10 years, but only 409 did.
The
authors concluded that using the Western model 'considerably overestimates
population risk for breast cancer incidence in Singapore'.
They
said: "For patients, early detection adds to the increased risks of procedures
such as breast biopsies as well as the risks of unnecessary treatment and
medical expenses.
"Over-diagnosis
also adds to patient anxiety and has social implications."
They
said four out of five large studies in the world have found no improvement in
survival when breast cancer was discovered at the pre-invasive stage, and even
among "invasive cancers", one in three mammograms is non-threatening.
The
study also found that women who had their first period before the age of 12,
have had a breast biopsy and had their first child after age 30 were at higher
risk.
Those
who have never borne children are also generally at higher risk than those who
have.
Dr Chay
Wen Yee, the first author of the study, said: "These study findings mean
that local doctors must place a greater emphasis on family history to
accurately predict a woman's risk of breast cancer, and indeed, of any cancer.
"A
carefully taken family history is a cheap, proven and easily available method
to determine proper timing and intensity of cancer screening."
Salma
Khalik
The
Straits Times
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