Screening mammogram controversy, Canadian National Breast Cancer Study, Lydia Pace MD MPH, Nancy Keating MD MPH, Biomed Central

Screening Mammograms Remain Controversial

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Screening Mammograms Remain Controversial

I am frequently asked my opinion of screening
mammography for early detection of breast cancer. Mammograms are not entirely free of risks. A
mammogram is an x-ray of the breast, and x-ray exposure is a known risk factor
for cancer development. This risk is downplayed by nearly all who promote
screening mammography, but in January 2009 researchers from Johns Hopkins
University, the National Cancer Institute, and Memorial Sloan-Kettering Cancer
Center concluded that the benefit of early cancer detection did not outweigh
the risk of radiation induced breast cancer in high-risk women under the age of

If the radiation risk of annual mammography screening cannot
be justified in women at the highest risk for breast cancer, what can one
conclude about the risk/benefit ratio in women who are at average risk? The
justification for screening mammography has been based upon the assumption that
early detection of breast cancer will significantly improve the survival rate.

This does not appear to be the case. While some studies have
shown that screening mammography saves lives, when taken as a whole, studies
comparing the breast cancer death rate in unscreened women to that of women who
have undergone routine mammography screening have failed to show a significant
difference. A 2009 review by Biomed
Central, reported a breast cancer survival percentage of 99.12 % in unscreened
women and 99.29 % in screened women between the ages of 40 and 65. The chance
that a woman will reduce her risk of dying from breast cancer by having a screening
mammogram was determined to be 0.034 %.

This week the Journal of the American Medical Association
published the results of a review of nearly 450 scientific articles on
mammography risks and benefits that appeared between 1960 and 2014. The researchers, Lydia Pace, MD, MPH, and
Nancy Keating, MD, MPH, concluded that the mortality benefit of mammography is
"modest" and the risks of harm from screening are
"significant." Editorials
accompanying the article agreed that the benefit of mammography is "less
than once hoped" and the potential harms are "greater than anticipated."

One of the longest running studies looking at the outcome of
screening mammography is the Canadian National Breast Cancer Study. It involved 89 835 women, aged 40-59, randomly
assigned to receive mammography screening or routine care without routine
mammograms. The results after 25 years
were reported in February 2014. The
findings for women aged 40-49 and 50-59 were almost identical. During the entire
study period, 3250 women in the mammography arm and 3133 in the control arm had
a diagnosis of breast cancer, and 500 and 505, respectively, died of breast

The study has been under attack ever since its findings were
first published in 1992. Proponents of screening mammography (primarily radiologists
and others who have a vested interest) argue that the Canadian study was "poorly
designed” and that advances in technology have rendered its finding
irrelevant. Nevertheless, the fact
remains that women found to have breast cancer by screening mammograms do not significantly
increase their chance of survival compared to women who perform monthly
self-breast examinations without mammography.

It is ironic that self-breast examination is no longer being
promoted to the degree it was prior to the advent of annual mammography
screening. Over the course of my career
I have seen women who detected breast cancer by self-examination months before
their annual screening mammogram was due.
I am also convinced that many women intuitively recognize that a cancer
is present even before it is detectable by a mammogram.

I am not opposed to the use of mammography to evaluate a
breast nodule or a concern that cancer is present. I even believe that mammography should be
repeated earlier than a year if a woman remains concerned that cancer may be
present after an initial study failed to detect any abnormality.

I do, however, believe that women should be given an
opportunity to decide for themselves whether to undergo a screening mammogram
rather than having it mandated by their physicians or insurance companies. They should be told that the radiation
exposure from annual exams will actually cause cancer to develop in a small
number of those receiving them and that there is a significant chance that the
study will indicate a need for a biopsy or treatment when no cancer is
present. Most importantly, women (and
men – men can also get breast cancer) should be instructed in the art of
self-examination and encouraged to perform an exam monthly whether or not they
choose to have screening mammograms.