November 24, 2000 (Ira Pilgrim)
You would be hard pressed to name another screening test that has been through as many randomized controlled trials as mammography. Yet, despite that, it continues to be dogged by uncertainties.
Barron Lerner, MD, Ph.D.
Around the turn of the previous century the results from surgical treatment of breast cancer were not very good. Johns Hopkins surgeon William Halstead devised an operation that bears his name. The Halstead radical mastectomy removed the breast, the chest muscles and all of the lymph nodes in the axilla(armpit). He achieved better results than anyone up to that time, and he was dealing with some good sized cancers. That operation is not done very often nowadays. (http://www.mcn.org/c/irapilgrim/toc21.html).Several very thorough studies showed that just removing the breast get just as good results, so radical mastectomy gradually went out of style starting in the late 1970s. My book The Topic of Cancer , which did not treat radical surgery very kindly, was published in 1974. Modified radical mastectomy replaced the Halsted operation. Now, I have been told, lumpectomy and radiation may be the method most in use.
One of the important bits of information, accumulated over the years, is that the chance of curing breast cancer is better if it can be treated before it spreads, if possible. The larger the cancer, the worse the prognosis. This is well established, although some very large cancers have been cured by surgery alone and some very tiny cancers have spread before they could be felt. However, the smallest cancer that is usually detected by feel is roughly half an inch in diameter. Some people theorized that if the cancer could be detected when it was still smaller, the chances of a cure would be enhanced; hence mammography, which can detect very small tumors.
The first large study of the efficacy of mammography was started in 1963 and involved 61,000 woman, age 40 to 64. Women over 50 who got mammograms had fewer deaths from breast cancer than those who didn't. With women 40 to 50 years of age, the results were equivocal. Despite many other trials which tested whether it is desirable to screen women 40-50 years of age, the results are still equivocal.
Some twenty or so years ago the American Cancer Society, under the leadership of radiologist Phil Strax, set out to convince every woman to have annual mammograms. The early phases of this program were a fiasco, with many x-ray laboratories performing mammograms. They were poorly read and some women had their breasts burned by the radiation. Things are much better now. Radiation doses are very much smaller and technicians and radiologists are much more experienced. One unfortunate side effect of this campaign was that women became much more fearful of breast cancer; for some, "terrified" would be a better word.
Everyone tacitly assumed that the smaller the cancer was when it was removed, the better the chances of a cure. If half an inch is good, an eighth of an inch had to be better. Now the results of a large Canadian study (39,405 women), started 21 years ago, on women over 50, are in and they call that assumption into question. All of the women in the study were taught to do breast self examination. They subjected women over 50 years of age to either an annual ten minute examination by a doctor or nurse, or an identical examination plus a mammogram (Miller, A.B., To, T., Baines, C.J., Wall, C. Journal of the National Cancer Institute 2000; 92:1490-9).
While there was no question that mammography detected smaller tumors than the examination did, the death rate of those women who developed breast cancer was identical in the exam-only group to the death rate in the mammography group. There was also the paradoxical finding that a few cancers were not detected by mammography, but were detected by examination. In other words, for women over 50, an annual thorough breast examination by a skilled examiner is as good, or perhaps better, than mammography.
This study is likely to cut into the income of the mammogram industry ($ 4 billion in the US). However, it may take at least 20 years for mammography to be relegated to the occasional special case. It took over 80 years for radical mastectomy to go away and the modified radical is still commonly done, despite the fact that it is no better at curing cancer than just removing the breast. As the headline of an article in the Journal of the National Cancer Institute says, "After 40 years, mammography remains as much emotion as science."
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