TOPICS > Health

Mammogram Guidelines

February 22, 2002 at 12:00 AM EDT


MARGARET WARNER: Do regular mammograms save lives? That question has been the subject of considerable controversy in recent months. For a quarter-century, doctors and cancer groups have recommended regular mammograms to screen for breast cancer, believing that early detection saves lives. Breast cancer strikes 190,000 American women and kills about 40,000 each year. Then, two years ago, a pair of Danish researchers announced that their analysis of all the major mammography studies to date provided no reliable evidence that regular mammograms reduce mortality.

The doubts they raised have led to widespread confusion about the procedure. Yesterday, the federal government stepped into the controversy. An independent panel of experts, convened by the Department of Health and Human Services, announced the results of its own analysis. Its conclusion: Mammograms remain an effective tool for preventing cancer deaths. Health and Human Services Secretary Tommy Thompson announced the panel’s findings.

SECRETARY TOMMY THOMPSON: Preventive service task force recommends, and I want to underscore that, recommends routine mammography every one to two years for women 40 years and older. This is an update from the task force 1996 recommendation on mammography, which recommended routine screening for women ages 50-69. The task force recommendation sends a very powerful and clear message about the value of mammography as an early detection tool that can help save lives.

MARGARET WARNER: Joining me now is Janet Allan, vice chairman of the U.S. Preventive Services Task Force. She is dean of the School of Nursing at the University of Texas Health Science Center at San Antonio.

MARGARET WARNER: Welcome Miss Allan. Expand — would you — on your recommendation as outlined by Secretary Thompson that your panel is reaffirming the value of mammograms beginning at age 40?

JANET ALLAN: Yes. That is true, Margaret. As you mentioned, the U.S. Preventive Services Task Force is an independent panel of 15 researchers and clinicians. And we are charged with developing clinical preventive — recommendations for clinical preventive services for the country. And so breast cancer screening is one of the areas that was on our agenda to review during this last session of the task force. And we use a very rigorous well-developed methodology for reviewing evidence on a variety of topics. And we used that methodology to look at the eight studies on screening mammography that constitute the– the evidence for whether screening mammography reduces breast cancer deaths. And we came to the conclusion that they did indeed reduce breast cancer deaths. And we came to the recommendation that there is a benefit for women to have a screening mammography every one to two years starting at age 40.

MARGARET WARNER: Let me first ask about the age 40 because that was a change from your own recommendation say six years ago. What new evidence came out that made your panel comfortable joining other groups in saying that starting at age 40 is a good time to start?

JANET ALLAN: Yes. And you’re correct that in 1996, which is the last time we did recommendations for a screening mammography, we did not find enough evidence to recommend for or against women having mammography starting at age 40. We did recommend it at age 50. What has happened is that the same trials, the same age randomized clinical trials are the evidence that we’re using, but we have longer follow-up information. We now have 11 to 20 years of follow-up data on women that were in those trials, which started as early as 1963 through the late 80s. And so we have more information to evaluate. The central question is — does screening mammography reduce deaths from breast cancer — and we came to the conclusion that there was a reduction of deaths from breast cancer if women started after age 40 to have a mammography.

MARGARET WARNER: Now these are the same eight studies, or at least seven of the eight are the same that the Danish researchers looked at. They said the studies were just too flawed. Did you not same the find flaws or did you find them and decide they weren’t relevant? How do you answer what they came up with?

JANET ALLAN: I think that’s a really important question because that’s created a great deal of the controversy. We’re all looking at the same studies. We say eight studies because there are two arms of a Canadian study. The Danish researchers put the Canadian studies together and called them one. So we’re still talking about the same studies. Again we not only, as I said, we use these rigorous methods in the task force, but because the Danish critique of these studies was first published in 2000, which is– and we were under– this topic was under review at this time.

We actually started looking at the topic in 1999. We were able to look at each of the criticisms that the Danish researchers had of the trials, and we did agree that we found the same flaws that they did, but we did not interpret the meaning of those flaws in the same way. The critical thing about a flaw– all trials are flawed, as you are aware. No trial is perfect. And what we were interested in is whether a flaw changed the end result of the trial or made the trial biased so the end result was not valid. And in our review of all the studies and all the flaws, we came to the conclusion that the flaws did not bias the end results, and that the end results are valid and that mammography does reduce deaths from breast cancer.

MARGARET WARNER: Now your report also talks about the risks — I think the word you all use– is the word harm from mammography. What are those?

JANET ALLAN: Again, I’m glad you raise that issue because one of the things the task force — there are harms from mammography. And one of the messages that the task force wishes to get to women in this country is that we want women to have the best information about both the benefits and the harms so that they can make their own personal choices about when to begin their first mammography and how often to have it. The benefits we’ve talked about, the 20 to 25 percent reduction in breast cancer deaths over a ten to 20-year period — the harms are that screening mammography is an imperfect test so that it has what we call false positives. Probably 3 to 6 percent of any mammography screening will be a false positive.

The good news of that is that 80 to 90 percent of false positives turn out to be benign. And if someone has an abnormal mammography, it does not mean they have breast cancer. It means that there is something on the mammography that does not look right to the radiologist, and they want to do further testing. So that because the test is not as sensitive as we would like, there are abnormal mammograms. And so those would have to be repeated.

So women have further mammograms. Sometimes they cannot tell from the repeat mammogram whether there is a tumor or not, and so that women have biopsies. Most of the biopsies turn out to be benign. Those are some of the harms that come with the screening and are of concern to many women. Some women would rather– they don’t see those as major harms because they would rather have ten mammograms to be sure that they don’t have breast cancer.

Other women really are much more uncomfortable about that. It does create anxiety and worry and so that they would rather have fewer mammograms. So that’s why we urge women to talk to their clinicians.

MARGARET WARNER: Back on the possible benefits, do you find evidence that mammograms, when they do detect a true positive, can lead to or can allow less radical treatment?

JANET ALLAN: I think that things have happened in parallel. I think as there has been more attention to breast cancer screening on a parallel course, the treatments for breast cancer– or the screening to actually identify very clearly what the tumor is have been improved. There are many improvements in the kind of screening tests that are done to determine if a particular abnormality is in fact cancerous or not. And they’re also beginning to develop some new treatments.

We know that the– as I said, there has been a reduction in death rates from breast cancer in this country. Some of that is attributed to screening, aggressive screening and women having more mammograms. Some of that is also related to better treatments, particularly the use of tamoxifen.

MARGARET WARNER: You mean the drug.


MARGARET WARNER: Given all the uncertainty, how firmly should women take this latest recommendation? I mean, if they’re barraged in the news with one thing after the next, how firm is this?

JANET ALLAN: I think the evidence is very good. And I think that what– I think the take home message to women is that we’re finding evidence that having a screening mammogram after age 40 will reduce breast cancer deaths. What we don’t have really clear evidence on is what exact age a woman, after 40, should begin to have her first mammogram. And we don’t have good evidence on whether screening every year is any better than screening every two years. And so that’s why again we urge women to talk to their clinicians and match their personal preferences with this evidence. But the evidence is very strong that it does reduce breast cancer deaths.

The other thing that I think is important to know is that the benefits from screening increase with age. Breast cancer is a disease of older women. Fifty percent of breast cancers occur after the age of 65. So there are fewer breast cancers to be– in women aged 40-49. One, I think, in sixty-six women will be diagnosed with breast cancer in that age group. So that that’s why we urge women to talk to their clinicians because there are — the benefits and harms — there are tradeoffs. And each woman has to make that decision.

MARGARET WARNER: Thanks Janet Allan, thank you very much, we have to leave it there.

JANET ALLAN: You’re welcome, Margaret. Bye-bye.