December 4, 1992
There are risks most of us accept. We drive automobiles,
knowing that we may be killed by them. The careful driver assumes
much less risk than does the careless one.
When I was a child, many physician's offices had a fluoroscope. Tuberculosis was common and the X-ray machine was the major tool of the physicians who diagnosed and treated that disease. Since the treatment wasn't worth much, early diagnosis, followed by rest and good food, was important. Patients with TB were regularly fluoroscoped to check the progress of the disease. I remember my father, who was healthy, standing behind a fluoroscope screen and the doctor pointing out his beating heart to me.
A machine was popular for fitting shoes that ran an x-ray beam through your foot --and into your gonads-- to see how the shoes fit. Kids would look at their feet, then call their friends to look, then call their parents. That some sired malformed children and some got cancer is not surprising. I doubt if any of them related their cancer or malformed child to their experience in the shoe store.
It never occurred to a man who had a deformed child that it was the result of his looking at the bones of his feet with an x-ray machine, nor would he attribute his cancer to the same thing. Why should he? How could looking at your feet as kid give you cancer as an adult? How could getting your chest fluoroscoped as a kid cause breast cancer in an adult?
It took a lot to get rid of those abominations as well as the mobile chest x-ray machines. Those days, fortunately, are almost gone, and a modern x-ray establishment uses high speed films, which require much less radiation to produce high quality pictures. When fluoroscopy is needed, there are image intensifier fluoroscopes that produce a good image with much less radiation. The physicians using these machines use leaded aprons and gloves. Patients are protected with lead aprons. But x-ray machines are very expensive, so some laboratories are reluctant to replace perfectly good old machines with new, low-dose equipment.
Before discussing mammography, I want to say something about x-ray in general. X-ray is part of a family of electromagnetic radiation called ionizing radiation, which means that it will break molecules. Among the molecules that can be broken by ionizing radiation are molecules of DNA, the genetic material. There are mechanisms in cells that can repair damaged DNA. The repair mechanism doesn't succeed all the time, which accounts for the occurrence of mutations and cancer.
There is a whole spectrum of ionizing radiation ranging from ultra-violet rays to very high energy x-rays. Ultra-violet can only penetrate the superficial layers of skin and can cause skin cancer and melanoma (a cancer of the pigment cells of the skin).
X-rays can be low energy (soft x-ray), which are absorbed by soft tissues such as breast; higher energy (hard x-ray) which are stopped by bone and tooth, and very high energy x-ray which is used to examine welds in steel.
When a dentist x-rays your teeth, using modern equipment, most of the soft x-ray is filtered out because it doesn't help to make a better picture and would be absorbed by the patient to his detriment. Most of the hard x-ray, that isn't stopped by tooth or bone, passes harmlessly through the body.
Mammography is soft tissue X-ray and more of the radiation is absorbed by the breast than in X-raying bones or teeth. When mammography first came into vogue in the seventies, the amounts of radiation used were alarming. Some women had their breasts burned by the radiation. Since then, much better equipment and high speed films have reduced the exposure considerably --but it is not negligible, nor can it ever be negligible. A significant amount of X-ray is absorbed by the breast. That's how it makes a picture; the radiation that is absorbed does not reach the film. Mammography as well as other x-ray procedures are not harmless and they can only be justified if it can be shown that more lives can be saved by them than will be lost as a consequence of the cancers caused by the radiation.
One estimate (Gohagen et al. 1986, JNCI 77:71-76) is that, in women who have one mammogram at age 35 and annual mammograms after age 40, anywhere from one in 7,000(with low dose equipment) to one in 1,000 women will develop breast cancer caused by the radiation. This is a very small risk when compared to the 1 in 10 risk of a woman getting breast cancer in her lifetime.
There is excellent evidence that mammography can detect tumors that are missed by the ordinary technique of breast examination, and that more woman will be cured as a consequence of early detection. There are also tumors that are detected by breast examination that will be missed by mammography.
Women getting only breast examinations were compared with women getting both breast examinations and mammography. One large studies in New York, showed clearly that mammography will significantly reduce the death rate from breast cancer in women. The results were most striking in women over age 50.
There used to be differences in the recommendations regarding the use of mammography. The National Cancer Institute used to recommend that it not be used to screen women under 35; that between age 35 and 39, that it be limited to women who have had breast cancer in one breast; in women 40 to 49, that it be used only in women who have had breast cancer or who have immediate relatives with history of the disease. In contrast, the American College of Radiology recommends a base line mammogram between the ages of 35 and 40 followed by mammograms at one to two year intervals. Both organizations recommended annual mammograms after age 50. The National Cancer Institute and American Cancer Society, as well as other organizations, now recommend the same procedure as is recommended by the American College of Radiology.
Since it is well established that the breast cancer producing effects of x-ray are much greater in younger women, everyone agrees that mammography should not be used in women under 35 years of age; except under special circumstances, such as checking the breasts of a woman who has had breast cancer. It is also agreed that mammography, as an adjunct to breast self examination, is potentially life-saving for women over 50, because the risk is more than balanced by its life-saving benefits. The question remains whether mammography is a good idea for woman in their forties. That is still being debated. All of the studies to date are flawed, so we really don't know. Some authorities believe that the decision should be made in each individual case by the woman and her doctor, and I agree.
Deaths from breast cancer have remained steady for the last 50 years. Despite the fact that more breast cancer has been cured, deaths from breast cancer have not gone down. The net effect of mammography and early diagnosis and treatment on deaths from breast cancer, to date, has been zero. We can conclude from this, that the benefits of mammography is being offset by something, or things, that is increasing the incidence of breast cancer. Could one element in that increase be mammography itself? I don't know, but it is a distinct possibility.
We have known for a long time that the probability of curing a breast cancer is, in part, a function of how early it is detected. A cancer half an inch in size has a much better chance of being completely cured by surgery than one that is an inch or larger. As a consequence, scientists have been trying to find ways of detecting tumors while they are still small and, presumably, more curable. At this time, mammography is the best bet for detecting very small cancers.
The challenge is to discover tumors and get them removed as soon as possible. This can usually be done if a woman does a good job of examining her breasts at regular intervals. Unlike mammography, breast self examination has no risk attached to it. It doesn't cost anything --and you don't even have to make an appointment. More important, it can, and should be done monthly instead of annually in ALL adults, at all ages. It is all benefit and no risk. Men also get breast cancer, but one man will get it for every 100 women.
After frightening the hell out of you, I am now going to advise you women over 50 to get an annual mammogram. Why? Because your chances of dying of breast cancer is so great that the risk from mammography pales in comparison. Another reason for scaring you is that there is a big difference between competent and incompetent mammography and there is no point in getting exposed to x-ray unless it does you a lot of good. Also, the price of a mammogram, which can range from $50 to over $250, is no indication of its quality.
Mammography can vary from x-ray laboratories that do an excellent job and use minimal doses of radiation, to labs that take your money and give you a false sense of security. What a woman should look for is the laboratory that will give her the best possible mammogram using the lowest possible amount of radiation. This means modern mammography equipment, used for mammograms only, with high resolution developing. The Xerox mammography system should be avoided because it delivers more than seven times the radiation as modern high-frequency film-screen mammography equipment --with seven times the risk of getting cancer from the radiation.
One good indication of competence is if the laboratory is certified in mammography by The American College of Radiology. The technician should be certified in mammography by The American Registry of Radiologic Technologists(ARRT). Under these conditions, the life-saving benefit of mammography far outweighs the radiation risk.
I am not very knowledgeable about the reading of x-rays, but I know for sure that a base line mammogram that is not available to the radiologist who reads that woman's subsequent mammograms is of little use, so if you get a mammogram, make sure that you can get it into the hands of the radiologist who looks at your next mammogram.
I am concerned that all of the hype about mammography will lead women to believe that mammography alone will protect them against dying of breast cancer. Mammography is an adjunct to breast self examination, not a substitute. Most breast cancers are still detected by the woman herself and a mammogram every one or two years is no substitute for monthly breast self examination. Nor is breast cancer detection alone a substitute for a complete physical including a pelvic examination and a Pap smear.
And most important, if you find a small lump in your breast, get to your physician. In women in their thirties, odds are 16:1 that it is not cancer; In older women the odds can drop as low as 3:1. The smaller the cancer is when treated, the better the odds of a complete cure.
This column is out of date. For a more up to date one on mammography, go to this link.
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