Half a year later, new mammogram guidelines remain controversial -- for good reason

It has been nearly six months since the U.S. Preventive Services Task Force (USPSTF) changed its recommendations regarding screening mammography for women. Controversial among the scientific community, the guidelines clearly have had the intended effect of decreasing the number of screening mammography exams across the country.

Briefly, the USPSTF recommended that women aged 50-74 have a screening mammogram every two years, rather than every year; that women 40-49 not undergo routine screening, and that, for women 75 and over, there isn't enough information to determine whether screening is useful. Why are these recommendations suspect?

The goal of any screening study is to find the disease earlier, when it is more likely to respond to treatment. For some cancers, like lung cancer, finding the cancer earlier isn't helpful, because usually it has already spread by the time it is detected. Early detection just means patients are aware of their cancer longer, not that they have a longer life. For other cancers, such as testicular cancer, the treatment is effective at most any stage, and early detection is not useful.

In only a few cancers -- such as of the breast, colon or cervix -- does screening find the disease early enough that treatment is useful and prolongs the patient's life. The goal has always been to prevent cancer, rather than diagnosis it earlier and treat it. Until we reach that point, screening combined with advanced treatment is the only method available to reduce the deaths from cancer.

The Task Force based its recommendations primarily on randomized control trials without looking at other means of assessment. While such trials are helpful, they have a major flaw. Once you are assigned to the control side or the study side, you stay there, whether or not you receive the treatment or exam. This is particularly true for screening mammography. If a woman is randomized to the screening side, but doesn't get the screening study, she still remains in the screening group. Conversely, if she is included on the control side, but feels screening mammography is useful and gets it on her own, she still stays in the control side. This "contamination" is significant.

There are other means of assessing the value of screening mammography. In Sweden, the county nurse is responsible for making sure that everyone follows the guidelines set by the county. Participation is more than 95 percent, and people are strongly encouraged to obtain a screening mammogram. Each county can decide whether to begin at age 40 or age 50. Women in their 40s had a 48 percent lower risk of death from breast cancer than those not screened. Similar results are seen in women from British Columbia, where there was a 40 percent decrease in deaths among women screened between ages 40 and 79, and a 39 percent reduction in women 40 to 49, during the period of 1988 to 2003.

What about screening every two years, rather than every year, in women 50 to 75? There is good data to show that screening every two years instead of every year will increase mortality 20 percent. This is even more true in younger women with breast cancer, among whom the cancers tend to grow and spread more rapidly.

Mammography is not perfect, and it does not detect every breast cancer. It does detect most of them, even in the 40-49 age group. Among 100,000 women in their 40s, there will be 200 naturally occurring breast cancers, of which over 150 will be diagnosed by mammography. There will be fewer than six cancers potentially induced by mammography over their entire lifetime, and those would be expected to be detected by continued screening. In addition, with the advent of digital mammography, detection is significantly improved in the women with dense breasts, who typically are 40-49. Digital mammography was not available for any of the clinical trials.

What about the anxiety, pain and suffering? Women are concerned when they have a positive result from a mammogram, just as men and women are concerned when their chest X-ray shows a nodule in the lungs. For every 100 screening mammograms performed, 10 will be called back for additional examination, of which six will be found to be normal. Two may be asked to return in six months for a follow-up exam, and two to three may have a biopsy. Only one in four to five of those biopsies will be cancer.

Biopsies are much different now, done with needles on an outpatient basis with local numbing medicine, usually performed in less than an hour with only minor discomfort. The vast majority of women can resume their normal activities, including work, immediately after the biopsy. In addition, the biopsies are frequently performed immediately after a recommendation, such that all of the diagnostic evaluation can be completed on the same day. This significantly decreases the anxiety that comes with mammography.

The task force doesn't talk about the pain and suffering in women who have cancer detected at a later stage, whose cancer would have been easily diagnosed a year earlier with screening mammography. Even if we said there was no improvement in mortality from screening (which there most definitely is), the ability to treat with less invasive surgery is important. Also, not having to get chemotherapy, lose your hair, become nauseated and experience complications or memory loss post chemo treatment is a huge plus for women.

Since the onset of routine screening in 1990, the mortality rate from breast cancer, which had been unchanged for the preceding 50 years, has dropped by 30 percent. The vast majority of women with breast cancer have no risk factors, so trying to determine which women to screen at age 40 is useless. Although there are fewer women in their 40s with breast cancer, 40 percent of the life years saved by screening are in that same group, because they will live more years after their diagnosis and cure.

Finally, there is excellent data to show that when all women are screened, the effect is far greater than the 15 percent reduction in mortality the Task Force used to make its recommendations.

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Joseph Tashjian, M.D., is a past president of the Minnesota Radiologic Society and currently chief of breast imaging at the Regions Breast Health Center.

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