The Downside of Mammograms

Posted on 24. Apr, 2017 by in Uncategorized

mamo1 by Chris Kresser

Mammography has been the medical industry’s “gold standard” breast cancer screening tool for nearly four decades, and the procedure has been pushed on women with great zeal by physicians, public health programs, and cancer organizations. However, mounting scientific evidence indicates that mammography may not only be far less effective than we have been led to believe, but that it also has numerous drawbacks that are affecting women on a massive scale. Read on to learn about the major drawbacks of mammography, what the research recommends for breast cancer screening, and about promising breast cancer detection alternatives.

A brief history of mammography

Mammography screening for breast cancer was first introduced in the late 1970s, and by the early 1980s, it had been widely incorporated into clinical practice. Prior to the widespread use of mammography, breast cancer detection tests were primarily based on breast self-exams and clinical breast exams performed by physicians. In the very early days of mammography, this test was used only in women at high risk for breast cancer; this included women who had a previous history of breast cancer, had a mother or sisters with breast cancer, or were over 50 years of age.

Fast-forward to the present day, and it is quite apparent that the use of mammography has increased dramatically. According to recent data, 66.8 percent of women over the age of 40 have had a mammogram within the past two years, an average of 15 million physician office visits have taken place per year in which a mammogram was either ordered or performed, and an additional 3 million outpatient visits have ordered or performed mammograms (1) .

Despite this massive increase in the use of mammography, there is a substantial body of research indicating that the widespread, overenthusiastic practice of mammography over the past few decades has had little to no effect on breast cancer mortality rates (2) . In fact, the research indicates that mammography screening may do more harm than good. Mammography has demonstrated a number of adverse effects, including breast cancer overdiagnosis, unnecessary breast cancer treatment, undue psychological stress, excessive radiation exposure, and a serious risk of tumor rupture and spread of cancerous cells (3) (4) .

Mammography screening leads to breast cancer overdiagnosis and overtreatment

mamo-overdiagnoseA 17-year study conducted in Denmark from 1980 to 2010 measured the incidence of advanced (> 20 mm in size) and nonadvanced (≤ 20 mm in size) breast cancer tumors in women ages 35 to 84 who either had received regular breast cancer screening over the years or had not received screening. If mammography was effective at reducing rates of advanced breast cancers, a reduction in the incidence of advanced tumors in the women who received the screening should have been observed.

However, no difference was found in the incidence of advanced tumors between the screened and unscreened groups. In addition, significant overdiagnosis of breast cancer was found in the screened group—approximately one out of every three invasive tumors and cases of ductal carcinoma in situ (DCIS) was found to represent breast cancer overdiagnosis. This meant that, due to screening mammography, healthy women were diagnosed with breast cancers. These women subsequently had to deal with the severe psychological distress of a cancer diagnosis, as well as the numerous physical harms of cancer treatment, when in fact their tumors were not cancers that necessitated treatment at all (5) .

A systematic review published several years prior found very similar results; in the United Kingdom, Canada, Australia, Sweden, and Norway, the overdiagnosis rate in organized breast screening programs was 52 percent, meaning one in three cancers in the screened population was overdiagnosed (6).

Further research has found that mammography screening has led to an increased detection of small tumors, but only a modest decrease in the incidence of advanced tumors. Many of the small tumors being detected by mammography represent breast cancer overdiagnoses. These small tumors are growths that, if left alone, would never progress to an advanced stage. However, mammography is diagnosing them as cancer, which is in turn causing countless women to be convinced to undergo cancer treatment, with all its harm and side effects, and without any benefit. In regards to the modest reduction in large breast tumors noted above, this reduction has been attributed to improved breast cancer treatment, not to screening mammography (7) .

Mammography selectively detects more favorable tumors

mammo3Mammography has a tendency to selectively identify tumors with favorable molecular features, which are features that make breast cancer treatment easier, offering a better prognosis. This is due to the fact that tumors with favorable characteristics tend to grow more slowly, so there is a larger window of time in which they can be detected by screening mammography. When screening mammography is used, these favorable tumors tend to be diagnosed long before they would begin to cause symptoms. This phenomenon is called length-bias sampling and refers to a statistical distortion of results that occurs when screening identifies disease cases before the onset of symptoms, making it appear as though survival time is increased for the particular disease due to screening. However, favorable tumors typically respond to treatment equally effectively at clinical presentation (when symptoms appear) as they do when diagnosed via mammography, so earlier detection through screening mammography does not translate into a reduction in breast cancer mortality (8) .

Breast tissue density affects the ability of mammography to successfully detect tumors. Low-density breast tissue makes it easier for mammography to visualize tumors than does higher-density breast tissue. In the fatty breast, mammography sensitivity is 98 percent; in the very dense breast, the sensitivity goes down to as low as 48 percent (9) . This is a significant issue because in postmenopausal women (the subgroup of our population that undergoes regular mammography screening), high-density breast tissue is associated with an increased risk of breast cancer as well as with the presence of tumors with more aggressive characteristics, such as larger tumors and estrogen receptor-negative tumors. The relative ease with which mammography detects favorable tumors has led to an overestimation of the effect of screening mammography on breast cancer mortality (10) .

Radiation from mammography may increase risk of breast cancer

The cumulative effect of routine mammography screening may increase women’s risk of developing radiation-induced breast cancer (11) . The current recommendations for mammography screening have led women to start screening at a younger age and also to receive more frequent screening; this has amplified the amount of radiation to which the breasts are being exposed, and the effects are not trivial. In addition, women who are exposed to radiation for other purposes or women who are carriers of the BRCA (breast cancer susceptibility) gene are at an even higher risk of experiencing adverse effects from mammography radiation (12) .

While not a direct reflection of the impact of mammography on breast cancer risk, other studies examining the effect of diagnostic chest x-rays on breast cancer risk have found that medical radiation exposure increases breast cancer risk (13) .

Mammography can rupture tumors and spread malignant cells

Mammography involves compressing the breasts between two plates in order to spread out the breast tissue for imaging. Today’s mammogram equipment applies 42 pounds of pressure to the breasts. Not surprisingly, this can cause significant pain. However, there is also a serious health risk associated with the compression applied to the breasts. Only 22 pounds of pressure is needed to rupture the encapsulation of a cancerous tumor (14). The amount of pressure involved in a mammography procedure therefore has the potential to rupture existing tumors and spread malignant cells into the bloodstream (15) .

Conflicts of interest and mammography recommendations

There is significant bias in the medical literature regarding mammography. This has led to significant breast cancer overdiagnosis and overtreatment, while also significantly influencing women’s perceptions about the purported effectiveness of mammography.

A literature review of 171 articles in the journal Evidence-Based Medicine found that a significant number of studies examining the effectiveness of mammography were published by interest groups and authors with vested interests in mammography screening. Scientific journal articles on breast cancer screening written by authors who have a vested interest in the practice of mammography tend to emphasize the potential benefits of mammography, while downplaying or outright rejecting the major harms such as overdiagnosis and overtreatment. Authors may have a vested interest in promoting mammography if they are receiving income from mammography screening programs or if they are contributing to scientific journals tied to political interest groups such as the American Cancer Society, which has financial ties with the makers of mammography equipment (16) (17) .

Due to conflicts of interest, the research being used to develop recommendations for mammography screening protocols is biased and is not a true representation of the efficacy of mammography for reducing breast cancer mortality. This has had a large-scale impact on the development of mammography screening programs (18) .

Perceptions of mammography benefits vs. reality

In a survey of U.S. women’s perceptions of mammography, 717 of 1,003 women (71.5 percent) said they believed that mammography reduced the risk of breast cancer deaths by at least half, and 723 women (72.1 percent) thought that at least 80 deaths would be prevented per 1,000 women who were invited for screening. However, based on U.S. mortality statistics, screening mammography prevents approximately one death per 1,000 women screened. Due to the influence of mammography propaganda, women’s perceptions of the effectiveness of mammography are overly optimistic and not even remotely a reflection of the true efficacy of mammography for preventing breast cancer deaths (19) .

Research also shows that women who are better informed about the risk of overdetection and overdiagnosis of breast cancer associated with mammography screening are less likely to participate in mammography screening (20) .

Informed choice is in jeopardy

mammography2Surveys indicate that women want to have balanced information and share the decision with their physician when it comes to whether or not they choose to go through screening mammography. However, many women have reported that they were never provided with information on the drawbacks of mammography, such as the risks of overdiagnosis, unnecessary cancer treatment, excessive radiation exposure, and potential for causing tumor rupture. The lack of balanced information about mammography provided for women jeopardizes their ability to make their own decisions regarding healthcare (21) .

Making decisions regarding mammography

What is the best decision to make in regards to mammography? This is a question that many women are likely wondering as criticism of this diagnostic technique grows. The truth is that guidelines for the recommended frequency of mammography screening and the age at which screening should begin tend to vary from one organization or committee to another.

The American Cancer Society states that women ages 40 to 44 should be given the choice to start annual breast cancer screening, women ages 45 to 54 should get mammograms every year, women 55 and older should switch to mammograms every two years, and screening should continue as long as a woman is in good health (22) . The U.S. Preventive Services Task Force has more liberal recommendations and suggests that the decision to start mammography screening before 50 should be an “individual decision,” that women ages 50 to 74 years should receive mammograms every two years, and that there is insufficient evidence that women over 75 should even receive mammograms (23).

In light of all this information, it is important to emphasize that mammography screening is a highly personal decision that should be made with the assistance of an unbiased physician and with full knowledge of the potential drawbacks. Women should also be fully informed about alternative breast cancer screening tools. Some of these alternative tools may be helpful adjunct techniques to use with mammography, and others may actually be suitable replacements for mammography screening.

Alternative screening tools

Alternative screening tools to mammography include clinical breast exams, digital mammography, ultrasound, and thermography.

  • Clinical breast exam (CBE) is a physical exam of the breasts done by a trained healthcare provider. Addition of mammography screening to clinical breast exam did not reduce the risk of mortality from breast cancer, indicating that CBE is a highly effective screening tool (24). However, CBE is typically still combined with at least one additional type of screening tool, such as thermography or ultrasound.
  • Thermography uses infrared technology to detect inflammatory patterns in breast tissue. It is noninvasive, does not emit radiation, can be done during pregnancy, and has the ability to effectively visualize dense breast tissue, unlike mammography. Thermography screening has demonstrated a high sensitivity and specificity. A high rate of false positives has been recognized as one of the drawbacks of this tool. However, these false positives may in fact be abnormal thermal patterns that are foretelling a future cancer that has not yet begun to grow to a physically detectable size. This theory is supported by studies in which thermography detected abnormal heat patterns in breasts several years before a breast cancer diagnosis was made. Thermography may therefore be a valuable screening tool due to its ability to detect functional changes in breast tissue before the onset of structural changes that occur in a cancerous state (26) (27) (28) .
  • Ultrasound is a noninvasive diagnostic tool that does not emit radiation and is safe to use during pregnancy. Ultrasound has demonstrated the ability to detect breast cancer at rates comparable to mammography, while also being very economical and patient friendly. A potential drawback is that ultrasound may not be able to detect tumors less than 1 cm in size. In addition, ultrasound is a highly operator-dependent tool and requires the involvement of a skilled sonologist. Nonetheless, ultrasound is a very promising emerging tool for breast cancer screening and may one day be a viable stand-alone alternative to mammography (29) .

Leave a Reply