For this patient, and many other women, mammography screening has become a double-edged sword. Responding to strong recommendations from the medical community, some 80% of women over 40 with no known risk factors for breast cancer dutifully undergo the annual screening. The conventional wisdom among advocates of regular screening is that with mammography, cancers are detected earlier and can be treated before they have a chance to spread. Often, we are told that middle-aged women who have annual screenings reduce their chance of dying from breast cancer “by about a third.” Early diagnosis is also cited as contributing to the fact that the five-year survival rate for women diagnosed with breast cancer is close to 90%.
Behind the Numbers
But scratch the surface of those figures and the benefits are not so clear. Fiver year survival rates are high in the U.S.. because so many woman are screened, and their cancers are detected very early. But that doesn’t mean they live longer than woman in countries where mammograms are not as common. Early detection does not guarantee a cure. Imagine that I live in the U.S. and at age 40, a mammogram shows that I have breast cancer; my twin sister, who lives in France doesn’t go for mammograms, and doesn’t discover she has cancer until she is 43. We both die at age 46. I survived for six years following detection, so I add to this country’s “five-year-survival” rate. My sister lived for only three years after her cancer was diagnosed. But we died at the same age. My only “advantage” is that I knew I had cancer for six years, while she carried this burden for only three years.
As for the idea that a middle-aged woman’s chances of dying from breast cancer is reduced by a third, first, keep in mind that the chances that breast cancer will kill you are not that big to begin with. Let’s say that in your age group, 3 out of 1,000 women will die of breast cancer over a 10-year period if they don’t go for screening. If they do have mammograms, only 2 out of 1,000 would die. The risk is reduced by a third—from 3 to 2—but we’re talking about only 1 woman in 1,000 being saved after all of them undergo mammograms, annually, for ten years.
In addition, in 2001, researchers from the Nordic Cochrane Center in Sweden published a review of relevant studies on mammography and found that screening was likely to reduce the relative mortality risk of breast cancer by 15%, not the 30% that most groups quote. Their conclusion: “For every 2,000 women [age 50-69] invited for screening throughout 10 years, one will have her life prolonged. In addition, 10 healthy women who would not have been diagnosed if there had not been screening, will be diagnosed as breast cancer patients and will be treated unnecessarily. It is thus not clear whether screening does more good than harm.”
Research also has begun to calculate the psychological downside to mammography. Many of us harbor a deep fear of being struck with no warning, of finding a lump, of receiving a diagnosis of “cancer” that instantaneously moves us from what Susan Sontag called the “kingdom of the well” to become citizens of that other place, “the kingdom of the sick.” We have all known someone who has been diagnosed with breast cancer; many of us have friends or relatives who have died from the disease. We have been conditioned to see regular mammography screening as a defense against breast cancer, something we owe our families and loved ones as much as ourselves.
More than one in ten women experience psychological distress after mammography, primarily because of the high rate of false positives and the attendant biopsies that result. The problem is that radiologists often have a difficult time distinguishing between cancerous and benign lesions on the film. In fact, some 90% of what looks like cancer in routine mammograms turns out not to be. And after ten years of routine screening, a woman stands a 50% chance of receiving a false positive and a call-back for more testing. The benefit of yearly mammography screening for low-risk, younger women age 40-50, is at least as equivocal. A panel convened by the National Cancer Institute in 1997 found that in this age group, less than one life would be saved for every 1,000 women screened for an entire decade. One problem in this younger group is that they are more likely to be diagnosed with fast-growing, aggressive tumors that show up in between mammograms, eluding early diagnosis. Another issue is that younger women tend to have denser breast tissue, making mammography less accurate and false positives and negatives more likely.
An Epidemic of Diagnoses
The problems of over-diagnosis and over-treatment have increased as advances such as digital mammography, computer-aided diagnosis and MRI scanning make screening more sensitive to tiny changes in breast tissue. Besides the shadows and microcalcifications that turn out to be innocuous artifacts of the imaging process, there has been a more than eight-fold increase in the diagnosis of ductal carcinoma in situ (DCIS), small “precancerous” lesions that are formed in the ducts from the milk glands. Often a mammogram will uncover these DCIS.
“We are witnessing an epidemic of DCIS,” says Nortin M. Hadler, a physician and professor at the University of North Carolina at Chapel Hill, in his book, Worried Sick: A Prescription for Health in an Overtreated America. That’s not because women are getting more cancers, he says, but because “U.S. women are getting more breast biopsies thanks to mammography. DCIS is the incidental finding of this exercise.”
How often DCIS, left untreated, would lead to invasive breast cancer is not known. But what is known is that at least 30% of these tiny lesions would not have caused a problem, and in fact, some proportion would have gone away on their own. Hadler bemoans the fact that in most cases, a diagnosis of DCIS leads to a lumpectomy, adjuvant radiation treatment and chemotherapy. “Finding DCIS and resecting DCIS and irradiating DCIS are enormous industries in the United States . . . I suspect that little of importance, perhaps nothing, would be lost if all these women with tiny lesions, only detected on mammography, never knew they had DCIS.”
Ambiguity and Vested Interests
Women looking for a clear, ultimate truth about mammography will be disappointed. The predominant view comes from a medical establishment that includes the enormous industry built up around screening and treatment. Radiology, pathology and surgery departments are big revenue centers for hospitals; some doctors have financial interests in the mammography centers where they refer their patients.. The world market for breast cancer therapies was estimated to be $11.3 billion in 2007, growing at 22% each year. The aggressive treatment of early-stage lesions like DCIS is a new industry in itself—with women at all points in the age spectrum, including elderly women, increasingly being diagnosed with the condition.. Cancer screening is also strongly supported by physicians who worry about the legal and personal ramifications of “missing something” in a patient who goes on to be diagnosed with late-stage disease.
“There will always be an asymmetry among testing proponents and detractors,” says H. Gilbert Welch, a physician and professor at Dartmouth Medical School, in his book Should I Be Tested For Cancer? “Testing proponents have a very strong interest (often financial) in promoting tests—much more so than the researchers trying to critically evaluate those tests. Proponents have powerful anecdotes, about individuals whose lives may have been “saved” because their cancer was caught early (if perhaps unnecessarily).”
In the end, the benefits of mammography are not as clear cut as women have been led to believe. The aggressive outreach for yearly screening does not reflect a realistic projection of how useful this technology is to women, especially those at the younger and older ends of the recommended spectrum. There is certainly little mention of the high rate of false positives, or increasingly, the chance that the cancer that is found might not be harmful and might even disappear on its own.
Most women do not know about the increased burden of unnecessary radiation and surgery—including biopsies, lumpectomies and mastectomies that results from this country’s zeal for cancer screening. This information might not—and should not—change the fact that many women still will want to be screened at all costs. But in the interest of making an “informed choice” women should know the real facts—or at least to be told that much of what they know about mammography is hyperbole. (For more about “informed choice” see this HealthBeat post) They should not be made to feel guilty if, with no family history of breast cancer or other significant risks, they decide to choose yearly clinical breast exams with less frequent mammogram screening.
Individuals Need a Chance to Make an “Informed Choice”
For groups that question the effectiveness of mammography, the goal is not to set limits on those women over 40 who feel strongly about being screened yearly. The real goal is to provide comprehensive, realistic information about mammography to help women and their doctors engage in the process of informed decision-making. This is a key component of patient advocacy; making sure that the choice to be screened is right for the individual based on her age, risk factors, personal beliefs and ability to deal with the psychological stress of false diagnosis.
Two years ago, the American College of Physicians issued new breast cancer screening guidelines suggesting that a routine annual mammogram for low-risk women in their 40s may cause more harm than good, and that the decision to be screened should be individual, based on a doctor-patient discussion of all the risks and benefits. These recommendations were published in the April 3, 2007 issue of the Annals of Internal Medicine, and deviate from the blanket guidelines issued by the American Cancer Society and many other groups that continue to recommend that all normal-risk women 40 or older get annual or biennial mammograms as well as physical exams to screen for breast cancer.
When it comes to women over 69, the ACP and other groups again stress the importance of individual decision-making. By contrast, the American Cancer Society continues to recommend regular mammography screening for women up to age 85 who are in good health, even though the new cancers that do appear in this group are usually slow-growing and the women are much more likely to die of something else before the breast cancer catches up with them.
A better recommendation comes from the authors of a 1999 article in the Journal of the American Medical Association, “Continuing Screening Mammography in Women Aged 70 to 79 Years,”
“Elderly women who are bothered by medical tests, visits to physicians, and the discomfort of undergoing mammography, or who experience significant anxiety waiting for test results, and who are willing to accept a very small incremental risk of death from breast cancer, may rationally decline screening.”
Some breast cancer advocacy groups also are taking a more individualized view of mammography. The National Breast Cancer Coalition Fund (NBCCF), whose membership includes cancer support, information and service groups, as well as women’s health and provider organizations, takes this thoughtful position on a complicated issue:
“The scientific evidence from randomized trials on the impact of screening mammography in saving lives is conflicted, and the quality of the individual trials limited. The National Breast Cancer Coalition Fund (NBCCF) believes, on the basis of recently published reviews, that the benefits of screening mammography in reducing mortality are modest and there are harms associated with screening. No individual woman can be assured that screening mammography will be effective for her, and from a public health perspective, the harms and public health costs of screening mammography may outweigh the modest benefits of the intervention. Mammography does not prevent or cure breast cancer, and has many limitations. Therefore, a woman’s decision to undergo a screening mammogram must be made on an individual level, based on quality information about her specific risk factors, and her personal preferences.”
Where should we go from here? It’s time to stop reevaluating data from the same seven large-scale studies on mammography that have been fodder for numerous review articles on the subject. By kicking out the results of some studies considered skewed or of poor quality—as the Danish researchers did in the Cochrane Study—a strong argument can be made that the risks of yearly screening for women under 50 exceed the benefits.
By going back to these same old studies—as the American Cancer Society and many other groups do–the opposite point can be made, over and over again.
Rather than recycling the old conventional wisdom, perhaps we should focus on the shortcomings that we now recognize as inherent in mammography and let them spur a concerted effort to improve the way we diagnose and treat breast cancer. This would mean spending money on research efforts to help differentiate between early-stage tumors and precancerous lesions that are likely to grow and become invasive and those that are likely to never progress—or even disappear. In the meantime, researchers should be also be exploring strategies such as “watchful waiting”—continuing regular screening on DCIS, but perhaps delaying surgical biopsies and further interventions until there are signs that a lesion is actually progressing.
In the end, “Mammographyy remain a pretty crude tool,” acknowledges the surgeon/scientist/ who writes Respectful Insolence under the nom de blog,“Orac.” . “The reason it persists is because it is inexpensive, at least compared to newer modalities. But unfortunately . . .newer, more sensitive modalities like MRI suffer from the same problem in spades, the MRI, it is even less able to distinguish between tumors. That’s why I tend to believe that ever more sensitive detection modalities are not the answer. Rather, the development of better molecular diagnostic tests that more accurately distinguish between aggressive tumors and tumors that are unlikely ever to trouble the patient will be far more likely to improve the “signal-to-noise” ratio and decrease the unwanted phenomenon of overtreatment.
Orac is right. Mammography is not the optimal solution for lowering mortalities from breast cancer. The sooner we admit that and start looking for better options, the sooner we will see real progress in reducing the number of women who are hurt—either by the dreaded disease itself, or by the fears that leads to “iatrogenic suffering;” misery caused, inadvertently, by medical treatment.