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Many women know something about mammography. You may have seen this e-mail I received some years ago:
Prepare for your yearly mammograms by lying on the cold concrete of a garage floor, stretching out their naked breast against the ground, and having someone back a car over the extended tissue.
For many women mammography is just one piece in the rituals of medical and self-care, encouraged by our physicians, or sought out by us. It is seen as a way to get some control over our fear: our fear of breast cancer.
Meanwhile, behind the scenes, mammography is a key weapon in the continuing "war" against cancer, and a technology whose value has been investigated and debated, often bitterly, for the last thirty-five years.
A recent article in the prestigious medical journal The Lancet, disputing the value of mammography entirely, is one more shot in the continuing debate.
It will not be the last.
The mammography issue matters for women's health in many ways. On the one hand, we need to know if mammography reduces the risk of premature death from breast cancer.
On the other hand, we need to know what mammography means for women's health in general. What does mammography represent in terms of goals, priorities, and hazards?
Does It Work?
Though a simple question, there has not been, nor will there likely be, a simple answer.
The main debate about mammography is over its value as a population-based screening technology. No one doubts that it can diagnose breast cancer in the individual woman who has a suspicious lump.
The Studies
Different studies have produced different results and much of the debate focusses on questions of method.
In the last decade, a heated debate has centred on age.
The majority opinion has held that mammography is of value for women over 50 (at about post-menopause). Several studies have shown breast cancer is more common in post-menopausal women, and the post-menopausal breast is less dense, making it easier to "read."
For pre-menopausal women, however, specifically women in their forties, there has been unruly debate about the merits of extending screening to this younger population, and little evidence to justify it.
The interesting thing about the recent Lancet article is that it says mammography is of no value for women of any age.
Because, Peter Gøtzsche and Ole Olsen say, mammography's value has not been demonstrated in experimental studies "screening for breast cancer with mammography is unjustified."
Why Mammography?
Why has so much time, energy and money been invested in using and evaluating mammography as a population-screening technology for breast cancer, and what does this mean for women's health?
Screening mammography is probably one of the most intensively evaluated health care technologies.
The hazards of mammography, as well as excess costs, derive from the technology's encouragement of medical intervention. By definition, screening tests are not fully accurate. There will always be a percentage of what are called "false negatives" and "false positives."
False negatives involve women who actually have cancer, but whose cancer is not identified by the screening test. False positives are tests finding something in someone that is not there.
In the world of mammography, the issue of false positives is a very big deal. Generally accepted estimates are that 4-8% of women will get a false positive result from each screen. This doesn't sound like much, but since women are encouraged to have repeated tests every year or more, the cumulative risk of a false positive result is actually very high.
Indeed, almost half of all women will receive a false positive test result after 10 screens (this is for women 40-69). Because of the lower incidence of breast cancer and the higher density of breast tissue, the risk of false positives is higher among younger women.
Delay Kills?
Many advocates in the women's health community feel the mammography issue has diverted attention from more pressing problems of preventing breast cancer.
The irony is that the mammography debates have been the most heated in the US where 40 million people are uninsured, and where recommendations about who should be screened come up against the harsh reality of who can be screened.
The intense focus on mammography is about more than just data on benefits and harms. Screening mammography is part of the dominant paradigm of cancer control.
There is a belief that 'early detection is the best prevention,' or more harshly, as a mid-1940s poster put it, "Delay kills."
But reality does not always support slogans, however catchy.
The "cancer establishment" - as the powerful collection of biomedical researchers, funders and lobbyists are sometimes called - has been enthusiastic about combating cancer through early detection for much of the twentieth century.
This is partly a response to the depressing fact that cancer still cannot be beaten.
But screening also responds to the financial and professional interests of agencies such the American Cancer Society, and those specialists whose services are used in screening mammography, such as radiologists.
We can expect to see more strategies for screening signs of cancer in the years to come.
Magic Bullet Medicine
Though the term "prevention" is used extensively in early detection campaigns, mammography is not really a form of prevention at all. Screening campaigns use high-tech "magic bullet" medicine and mobilize biomedical communities.
Efforts to tackle the fundamental causes of cancer, such as environmental carcinogens, do not get the attention of biomedical interests.
In an era in which people are encouraged to take personal responsibility for their health, and when knowledge is seen to be inherently valuable, it's hard to express scepticism about mammography's merits.
But there is, I would suggest, much to be sceptical about. Mammography has been advanced as a tool of health promotion - potentially able to reduce mortality. It may do so, but not without influencing health care priorities, and not without harms.
Raising Fear
Raising awareness of breast cancer to encourage compliance with screening guidelines also raises fear. With its high rates of false-positive tests, screening mammography promotes vulnerability as well as health.
It also promotes the belief that individual women are personally responsible for their health, a belief that encourages guilt if individual women are "non-compliant" with screening guidelines, or if they develop the disease.
The case of screening mammography highlights the dilemma of the lag between adequate knowledge and the need to act.
That gap is growing, not shrinking, as new studies are showing breast cancer is a set of distinct diseases some linked to genetics, and some potentially benign.
Screening Hazards
If the statistical data available to us is unclear on the merits of screening mammography for the "average" woman, it is even less informative about the benefits and hazards - like potential radiation hazards - of mammography for women.
After more than thirty-five years of study and debate, it seems fair to suggest that evaluations of screening mammography have helped institutionalize it, more than evaluate it.
The calls for new data and more studies, made in the face of uncertainty, seem designed to ensure its use will spread. Or it will at least postpone decisions to change priorities - to focussing on prevention, for example.
As the women from Breast Cancer Action in San Francisco put it in a recent ad campaign: "Breast Cancer: Do you want to be aware of it? Or do you want to prevent it? There's a big difference."