My organization, the Center for Medical Consumers, is founded on the belief that people should be encouraged to base their medical treatment decisions on the published evidence. We also believe that screening decisions should be held to the highest standard of evidence because they affect healthy people.

When the National Cancer Institute (NCI) announced its 1993 decision to withdraw the mammography screening recommendation for women in their 40s, I believe that it made the correct judgment. But this didn't seem to change many opinions. Women had already been sold the idea that early detection of breast cancer at any age virtually guarantees cure. The two most common reactions I heard from women at that time were: "I'll still have mammograms just to play it safe" and "What can we do to protect ourselves, if they take away mammography?" To many, it seemed inconceivable that finding a tumor early could be anything but beneficial. At the very least, many women reasoned, finding a breast cancer early would mean a less drastic treatment--a widespread misperception. National breast cancer trials in 1986, for example, found that a lumpectomy and radiation are as effective as mastectomy for women with tumors as large as four centimeters (or even with a tumor that has spread to the lymph nodes).

But facts such as this didn't seem to matter. In a scenario I have observed many times, be it a public forum on breast cancer or a radio show, the speaker who points to the lack of scientific evidence to support mammography screening for younger women invariably triggers this response from a member of the audience: "How dare you say that mammography has no benefit to women in their 40s, my breast cancer was discovered on a mammogram last year when I was 43. Now my life has been saved."

Overselling. The overly optimistic opinions surrounding mammography screening's value to women in their 40s are the direct result of promoting a technology to the public before there was clear scientific evidence proving benefit. In the early 1970s, before there was any scientific evidence to prove mammography's benefit to younger women, the American Cancer Society (ACS) and the NCI began to promote screening for all women over the age of 35. The message to the public was--and still is--"breast cancer is curable, if detected early enough." What was merely a hunch on the part of ACS and NCI was presented to the public as established truth.

While a woman's doctor may be the most influential factor in determining whether she will undergo mammography screening, the most influential source of information for the lore surrounding mammography screening--for the overly optimistic expectations surrounding mammography--is the ACS. The ACS has a long history of overstating the case for early detection, of using five-year survival statistics to imply cure, of recommending screening tests before there is scientific evidence to prove safety and efficacy, and of not warning of mammography's downside, specifically the uncertainties surrounding ductal carcinoma in situ (DCIS).

In 1977 the public learned about these so-called "microscopic cancers" that caused 64 women to be misdiagnosed as having breast cancer in one set of trials; 37 had undergone mastectomy. Quite a revelation. No one ever warns the public about finding a cancer so early that pathologists aren't sure that it's cancer. And here we are 20 years later, and pathologists are still trying to determine the natural history of the different subtypes of DCIS in order to avoid overtreatment.

Now, there's a new generation of women in their 40s who were too young at the time of those 1977 headlines to be concerned about mammography-related misdiagnoses. After all, breast cancer in that era was an older woman's disease. Women now in their 40s have been "raised" on the public health message that "breast cancer is curable if found early enough." In other words, cure is simply a matter of finding breast cancer early.

Yet in 1980, I would come across a review of all published breast cancer trials in The New England Journal of Medicine which found that 26%-35% of all women diagnosed and treated at Stage I developed metastasis anyway and died within ten years of their mastectomies. This is just one of many contradictions I would find between the "public education" message to women and the published evidence.

In 1985, we saw the start of breast cancer awareness activities, initiated and largely sponsored by Zeneca, the manufacturer or tamoxifen, a cancer treatment. Now it is the corporate ads like those of DuPont and General Electric (GE), makers of mammography-related equipment, that feature the same old misleading statistics. A recent GE ad for breast cancer awareness month, for example, claimed "a remarkable 91% cure rate" for its new, improved mammography equipment. What does this mean? The figure refers to the proportion of women who now live for at least five years after diagnoses and treatment--not an accurate measure of cure.

These corporate ads come cloaked in the aura of public service announcements (PSAs). And frankly, in terms of half-truths, I don't find them to be any different than the real PSAs sponsored by the ACS or the American College of Radiology. The depiction of young women in these ads, the use of misleading "one in eight" and "one in nine" statistics, which refer to risk over a lifetime, not during a woman's 40s, and the magazines and talk shows featuring personal stories of young breast cancer survivors have all contributed to the impression of breast cancer as a young woman's disease. Put this heightened awareness together with the exaggerated "public health message"--early detection equals cure--and you have a lot of women out there who think that a mammogram is the only thing that stands between them and imminent death from breast cancer.

Danger of Misdiagnosis. Mammography proponents invariably frame the debate in this manner: what's the harm of anxiety over an abnormal mammogram or a biopsy compared to death from breast cancer? Well, we don't know whether any deaths are prevented, and many women (including those over age 50) do not fully understand the third possibility associated with mammography screening: misdiagnosis of cancer--the over-reading of atypical benign breast disease as carcinoma in situ, or of in situ disease as invasive cancer. Such diagnostic errors have occurred in several major trials where pathologists would be expected to be more expert than those in the real world. I have met many a woman who has had a mastectomy for DCIS, who regards herself as a cancer survivor, who worries about recurrence like every other cancer patient, who believes her daughters are at high risk, and who has no idea of the uncertainties that surround her diagnosis or that evidence suggests that only some cases of DCIS will become invasive cancer.

Most women today with a diagnosis of DCIS come to our center knowing something about the controversies surrounding it. But the point is they hear it for the first time at diagnosis, not before they consent to screening in the first place.

High False Negatives. Traditionally, cancer survivors become evangelists for screening, but I've detected less enthusiasm of late. Every breast cancer activist I know is a woman diagnosed in her 40s. These women know firsthand about mammography's other problem: its high false-negative rate for younger women.

Women who have a mammogram every year during their 40s run a 30% chance of being told that the X-ray shows an abnormality, even though their breasts are normal. The vast majority of these women then will have unnecessary biopsies, some even mastectomies.

New evidence from Sweden shows a 24% reduction in breast cancer mortality. For nearly a year, radiologists have been portraying this finding to the public as the proof that now ends the controversy. But what, for example, does the reduction in "subsequent" mortality actually mean? (The public never hears that qualifying word.) Is this finding an argument for starting screening at age 40, or for delaying it until age 50? How does a woman weigh the 24% reduction in subsequent mortality against her odds of misdiagnosis? Does this mean that everyone who undergoes mammography screening can reduce her personal odds of dying of breast cancer by 24% (which is how most people interpret such a statistic)?

Perhaps it is fairer to put it this way: Mammography screening will result in a prolonged life for 24% of women with breast cancers. The majority of women whose cancers are found on a mammogram, however, will be unaffected by early detection, either because they have an aggressive, fast-growing cancer or because the tumor is so slow-growing, the women would enjoy long-term survival whether it was found early on a mammogram or later, once a symptom appeared. Some women will be falsely assured that they are cancer-free.

I have contacted several advocacy organizations and heard variations on this theme: "We'll continue to have mammograms, but researchers must find better ways to detect early breast cancers because mammography does not help most women. We need to know more about what causes breast cancer." Mammography may be the best detection tool we have, as the PSAs constantly remind women, but it's just not good enough.

The recent Consensus Panel, by educating women and their doctors about what mammography can and cannot do, may bring to the topic a large dose of reality.


By Maryann Napoli

Ms. Napoli is associate director of the Center for Medical Consumers in New York City. This article is adapted from her presentation before the National Institutes of Health's recent Consensus Panel on breast cancer screening.

Share this with your friends