Recently, an article was published in the New England Journal of Medicine questioning the utility of mammogram screening for prevention of death from breast cancer.
The authors were research professor Archie Bleyer MD at Oregon Health and Sciences University in Portland, an oncologist who was chief of pediatrics at MD Anderson Cancer Center and H. Gilbert Welch MD, MPH, a professor at Dartmouth Medical School. The article examines the ability of mammograms to prevent late stage breast cancer by diagnosing and treating breast cancer early as a result of detection by mammograms.
They found that mammograms do detect lots of breast cancer, but when we compare women during the years 2006-2008 when mammogram screening was widely practiced to women during the years 1976-1978, there was no difference in the incidence of the really nasty breast cancers, ones that had spread beyond the regional lymph nodes, and only a small decrease in the less nasty but still significant regionally metastatic cancers. Many, many women were treated for breast cancer but only a few were saved from dying of late stage disease with mammogram screening.
Their evaluation was carefully done, making assumptions about the increase in rates of breast cancer over time that were designed to make the results of having a mammogram more favorable. They concluded, somewhat generously, that “ Women should recognize that our study does not answer the question “Should I be screened for breast cancer?” However, they can rest assured that the question has more than one right answer.”
Mammograms are x-rays of breast tissue and were first introduced by a German surgeon named Albert Salomon in 1913 when he examined mastectomy specimens with x-rays. Mammograms were used rarely before 1978 when widespread use of mammography was introduced in an attempt to identify and treat breast cancer early to reduce mortality and morbidity. The procedure has been controversial since 1978. The first objections regarded the danger of radiation to the breast. A mammogram is performed by squashing a breast between two plates and passing x-rays through it. A digital mammogram detects the x-rays with digital detectors and creates an image on a computer monitor. A film mammogram creates an actual negative on a piece of photographic film. These techniques are equally sensitive but digital machines are replacing film machines due to the overall convenience of storage and communication of images. The dose of x-rays with a typical digital mammogram is 3.9 milligrays, the same as for a film mammogram, and about 4 times the radiation dose of a chest x-ray. It is a small dose and is probably not a significant danger.
After initial worry about radiation, very reasonable concerns remained about the quality of mammograms and mammogram readings. In 1992 the Mammography Quality Standards Act was passed to assure that facilities that performed mammograms were accredited by the FDA to be of adequate quality.
Mammograms are very big business. I can’t find out how big, but if there are about 40 million women between the ages of 50 and 75 and half of those get mammograms at a cost of $100, that would be 4 billion dollars spent on mammograms alone, not to mention repeat mammograms and other technology to further identify actual breast cancer. If I am off by a factor of 4, that’s still 1 billion dollars. It is a big deal to write an article questioning the utility of this test. Any move away from a recommendation of yearly mammograms starting at age 40 or 50 is met with outrage. Still, articles and studies continue to demonstrate that the benefit of screening mammography is limited.
Norway has been extensively studied with regard to mammogram screening because they keep excellent records and have had a staggered approach to universal mammogram screening for women. Over the last 20 years multiple studies have come out of Norway suggesting that breast cancer is overdiagnosed by mammogram. Overdiagnosis is what happens when we find a breast cancer that would never have caused harm if it had not been detected. Some cancers do not kill people and are probably taken care of by a healthy immune system. In an article published last April, a study group evaluated the data and estimated that, of all the breast cancers diagnosed, about a quarter of them would never have caused harm. This week’s article concurred, but suggested that number may be as many as 30% and that over a million women have been diagnosed with breast cancer since the inception of screening who would never have been affected had they not had mammograms.
But, one might ask, is it really a big deal to be diagnosed with breast cancer that would not have hurt or killed you? Yes. It is actually a very big deal. The British Medical Journal reported that 50% of women were depressed in the year after they were diagnosed with early breast cancer, the type of breast cancer most likely to be overdiagnosed. But we don’t really need studies to tell us this information. It is clear after treating women with breast cancer that they are profoundly affected by this diagnosis, feeling ugly, self conscious, maimed. Treatment complications include disfigurement, chemotherapy side effects, infection, chronic pain, to say nothing of astronomical monetary costs.
Still, breast cancer kills, and fewer people die of it now that mammogram screening has become standard. How do we explain this? Some of it is due to mammograms. We are detecting lots of breast cancer early. Some of it we should be detecting early and some we should not. Still, some early breast cancers would have become late, bad, killer breast cancers. The study suggests that there are not many of these, but there are definitely some. The treatment of breast cancer has also gotten much better. People who used to die of metastatic breast cancer now remain on chemotherapy and remain in remission for many years, and some are cured. It is undoubtedly because of the huge increase in breast cancer awareness that therapy has improved, and likely the million women who were overdiagnosed were important in helping to pioneer excellent treatment.
What is a woman to do? What is a doctor to do? I think it might be good to start with recognizing that a decision not to do mammogram screening is not tantamount to a death wish. We give women who reject the recommendation for regular mammograms a really hard time, and that is neither fair nor evidence-based. Mammograms are quite good for evaluating lumps, especially in older women. They are also good for giving peace of mind, since a negative mammogram suggests (but does not prove) that a woman does not have breast cancer.
There may be a subset of women, those at particularly high risk of cancer for instance, who would be very wise to have regular mammograms. There may be technology that can help us identify which breast cancers need treatment and which do not. Tests that detect more breast cancers, such as MRI and PET scanning may not be particularly helpful in this situation unless they can reassure us that some breast cancers are of no significance. If we accept that medical resources should be limited, we might look at places where money now used for universal mammogram screening of women might be more effectively spent.
Janice Boughton is a physician who blogs at Why is American health care so expensive?
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