Breast cancer screening
not always best choice
Careful thought needed
Breast cancer screening through regular mammography is not necessarily
of benefit to women between 40-49 years of age, according to Dr. Harold
C. Sox, senior vice-president of the Annals of Internal Medicine.
Dr. Sox spoke at the medical school Oct. 18 as part of the Atlantic Provinces
Speakership Program in Internal Medicine.
Outlining conflicting results from studies done in recent years about
the benefits of mammography in terms of preventing death from breast cancer,
Dr. Sox said that a recent Canadian study published in the Annals showed
that screening had no effect on the rate of breast cancer death in women
from 40-49 after 12 years of follow-up.
“In my opinion, this is a study you can not ignore – it was
very high quality.”
Although previous studies have shown different results, Dr. Sox has compared
the studies and feels that the difference is not significant.
“In my opinion we’re not sure whether screening younger women
for breast cancer is going to affect the death rate from breast cancer
very much, and I personally believe that screening women as a matter of
routine is not a good idea. The decision to screen is one which should
be made by the woman and her physician after the woman has had a full
briefing on the potential benefits and the potential harms of screening.”
Although most women in the U.S. and Canada do opt for regular mammography,
Dr. Sox would like to see family physicians play an active role in informing
women about the evidence.
“The harms of breast cancer screening are potentially substantial.
False-positive mammograms are relatively frequent – if a woman is
screened for 10 years for breast cancer, about 50 per cent of women will
have at least one false-positive mammogram which can lead to biopsies,
further follow-up tests and a lot of worry. In addition, there’s
a form of breast cancer called ductal carcinoma in situ (DCIS), a common
form of cancer in women of all ages. It is not always invasive, and yet
it’s become the standard of care to treat women with DCIS in the
same way as a woman with invasive breast cancer. Mammography is very good
at picking up DCIS, and so we have a situation in which some women with
positive mammograms will have DCIS and will be treated as if they have
invasive breast cancer, and yet probably a substantial number of those
women would never develop invasive breast cancer.”
Dr. Sox said potential harms of screening for breast cancer need careful
thought.
“There are some really big unknowns still to be understood before
we can do a better job of deciding which women should be screened for
breast cancer when they are young and which women should not be.”
As for regular mammography for women over 50, Dr. Sox wholeheartedly endorsed
this. “Almost everybody is in agreement that screening for breast
cancer in women over age 50 will reduce the rate of death from breast
cancer by about 20 per cent. I personally believe that in older women
we need to be very attentive to the need for people to get screened, whereas
in younger women we need to be attentive to the need for a good discussion
and an individualized approach to decision-making.”
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