Mammograms: Still a Good Idea?

In October an article in the Journal of the American Medical Association raised serious questions about the value of mammography as a way of saving women’s lives. To doctors and researchers this was not news, but it made headlines, and public anxiety rose.

What happened next sowed confusion, incredulity, and outrage, at least among many women trying to follow the argument. In November, unaware that it would stir up a hornet’s nest, the U.S. Preventive Services Task Force announced new guidelines about mammography: it recommended against mammograms for most women in their forties, and said women age 50 to 74 should get mammograms only every two years, instead of annually, unless they are at high risk (notably those who have a genetic mutation linked to breast cancer). It said the data showed that biennial screening saves nearly as many lives, but produces only half the number of false-positive results and their negative consequences, such as needless biopsies. The Task Force remained silent about mammograms for women 75 and older because of insufficient data. It went on to advise doctors not to teach women to do regular, systematic self-examinations of their breasts, for lack of evidence of benefit.

If you read this newsletter regularly, you have heard of the Task Force. It is a panel of experts appointed by the government to evaluate evidence on a given question and make recommendations. There are different panels that study dozens of medical issues, from dental X-rays to blood tests for diabetes. They offer interpretations and recommendations, not legislation, though some insurers base their coverage on these recommendations. Many people erroneously thought the Task Force had the power to change policy. Many people also assumed, mistakenly, that the new guidelines were somehow connected with the debate in Congress about health-care reform—as a way to control costs by reducing care for women. Opponents of reform once again attacked the “bureaucrats.”

And disagreements among experts multiplied. The American Cancer Society said it would stick to its recommendations for annual screening beginning at age 40. Some claimed the evidence for cutting back on frequency was inadequate. Still others welcomed the new recommendations on the basis of reduction of harm from mammography, such as false-positive results leading to biopsies and anxiety. Some cited cost savings.

Whether you look upon all this as healthy debate or simply a confusing and disheartening mess and a threat to your well-being may depend on your experience. Many women believe that their lives have been saved by mammography—not to mention self-exams. Some women may have concluded from all this fuss that there is no point in ever having another mammogram. Women who dread mammograms no doubt welcomed the chance to have fewer of them. Others felt betrayed and endangered.

And others merely wondered, “Why do those experts keep changing their minds?” Here is our take on all this.

What this was all about

The Wellness Letter has always endorsed annual mammography as a means for the early detection of breast cancer. For a time we advised women to do regular self-exams—a position we reversed in 2006 because of lack of evidence for benefit. Unlike the American Cancer Society we have recommended that annual screening begin at age 50, not age 40, except in certain cases to be determined in consultation with a physician.

Two cancer screening tests—the Pap test and colonoscopy—clearly save lives. There’s no argument about their benefits. About other tests, such as PSA (for prostate cancer) and lung cancer screening, there’s a lot of argument, and no clear evidence of benefit. Mammograms fall in the middle of this spectrum. They do save lives—just not as many as we hoped. According to the Task Force, to save one life in the 50-to-59 age group, 1,339 women must be screened for 10 years (337 women in the 60-to-69 group), and that will mean thousands of screens, which then result in hundreds of biopsies, and many cancers treated as if they were life threatening when they are not. The specific numbers have been debated and questioned as the experts argue about statistical models, but the bottom line is clear: mammography is not a very good test.

While preaching the benefits of mammography, the Wellness Letter has also discussed its shortcomings. One drawback is that if there is a cancer, sometimes the test misses it. This is called a false-negative result. False-positives occur, too, in which the test sees something suspicious, leading to a biopsy with all the attendant anxiety, discomfort, and expense, and the tissue turns out to be benign.

These are not the only problems. Here are two others:

• All, or virtually all, breast cancers start in the milk ducts—these are called ductal carcinoma in situ (DCIS). Some will never develop into invasive cancer, and it would be better, obviously, not to treat those cases. But there is no way to determine which will simply stay small and local. Thus an unknown number of women who undergo surgery, radiation, and medication for DCIS would never have developed invasive cancer in the first place. This is known as “over-diagnosis” and “over-treatment.” At present that’s really the only option. Women and their physicians are almost never willing to take a “wait and see” attitude about breast cancer. And nobody recommends that they do. At least the treatment for DCIS is less extensive than for invasive cancers.

• Some cancers that will prove invasive and thus deadly may start to develop and spread between mammograms; these may not be responsive to treatment. Thus, as we all know, some women who faithfully get mammograms still die from breast cancer. The troubling part about this is that it raises the possibility that early detection—and the whole rationale for screening—may not work against some cancers.

Now what?

If you are wondering what to do about mammograms, here’s our advice. We believe mammography saves lives, and we think women should continue to have them. But . . .

• This controversy is a process, not a crisis. The arguments about mammograms have been going on a long time. You and your doctor need to discuss your specific needs. If you want annual mammograms, no one is telling you not to continue. Women at high risk because of a strong family history, previous biopsies, or a genetic mutation need professional advice.

• However, on the basis of the evidence cited by the Task Force, for most women, it would make sense to switch from annual screening to every two years. The evidence shows that mammography every two years saves nearly as many lives as annual screening. Annual screening discovers more cancers than screening every two years, but it also finds more things that turn out not to be cancers—false-positives. In addition, some of the cancers found will be slow-growing, so biennial screening will find them in time to treat them. And it will save many women the pain and expense of needless biopsies and possibly chemotherapy, radiation, and treatment of cancers that would never have become life-threatening. Again, we emphasize that a consultation with your physician is a wise first step.

• A systematic monthly self-exam is not forbidden, even if not recommended. Do, however, be aware of changes in your breasts or the onset of symptoms, such as a lump or nipple discharge, and get medical advice immediately.

• We continue to believe that screening for most women should begin at age 50, not 40. The 50-to-74 age group has the most to gain from mammograms. The incidence of misleading results is considerably higher in women in their forties. But again, this is a matter for each woman and her physician to decide.

• Every state except Utah requires insurers to pay for mammograms for women starting at age 40. Medicare pays for annual mammograms, with no upper age limit. The government and industry officials have hastened to say that they have no intention of changing their policies based on the Task Force findings. Nothing in the proposed health-care reform legislation would alter this.

Editorial: The Mammogram Mess, by Dr. John Swartzberg

The dispute about when women should have mammograms has been loud and confusing (see page 1). I for one am glad to see a public debate. Yet it has almost drowned out another long-overdue discussion about mammograms. How good are they?

In November an article in the Journal of the American Medical Association, with Dr. Laura Esserman of the University of California, San Francisco Medical School as the lead author, brought up an inconvenient truth. Though mammography has been vigorously promoted, and billions have been spent to set up this vast testing industry, it is a relatively poor way to screen for breast cancer. Since it was introduced on a large scale in the 1970s, there’s been uncertainty about how many lives it saves. The data have always been confusing.

One thing is clear, though: if you have to argue for years about how valuable a test (or treatment) is, you can be sure it’s not very valuable. Good tests, like the Pap test and colonoscopy, prove out quickly and clearly. The death rate falls substantially. The mortality rate from breast cancer has been falling in the last 20 years, and some of this is clearly due to mammography—but the drop has been gradual, and it has come at a great cost in false results and unnecessary treatment.

Among the serious concerns: Why has the increased detection of early cancers via mammography not had a greater effect on reducing the incidence of very aggressive cancers and thus death rates? We all know of women who had annual mammograms and died anyway. Also unsettling is the fact that early cancers uncovered by mammograms may turn out to be “indolent” (that is, very slow growing—and some may even go away) and not need treatment at all. But we don’t know which ones these are. After decades of research, we still cannot say for certain what causes breast cancer, and why sometimes it grows quickly and spreads, and other times it remains harmless.

For now this imperfect tool, cumbersome and expensive, with its limited benefits and clear downsides, is the best we have for screening. It makes sense to understand the limitations of mammography but to continue to use it until better methods come along. We agree with the new guidelines—and so does Dr. Esserman, who recently told us, “the cancers that will benefit most from screening arise in women age 50 to 74, and screening every 18 to 24 months is sufficient to provide benefit.” Please see our article for a more detailed discussion of these matters.

But we must not settle for what we have. We need better ways to screen for breast cancer. We need more precise tests for determining the nature of a cancer when it is detected—that is, for distinguishing an indolent breast cancer from an aggressive one. When aggressive cancer is detected, better treatments must be devised for it. Researchers must continue to look for new approaches, rather than arguing about old ones.

UC Berkeley Wellness Letter, February 2010

Click here to read more wellness information at www.wellnessletter.com.