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Breast Cancer Screening and Overdiagnosis

Breast Cancer Screening and Overdiagnosis

2017 - 01 - 16 | Author: Susan Silberstein, PhD

mammographyThe latest study to raise questions about the value of screening mammograms was published online last week by the Annals of Internal Medicine. A group of Danish researchers followed women ages 50 to 69 who were screened and not screened and analyzed Danish breast cancer registry data for those diagnosed with invasive breast cancer from 1980 to 2010. Their conclusion: Mammographic screening did not reduce incidence of advanced tumors, and one out of every three breast cancers found in the screened women was overdiagnosed.

Overdiagnosis is finding medical information that does not benefit the person, and which may cause harm, especially if it leads to overtreatment. In this case, overdiagnosis means detection of a tumor that likely would never have caused any symptoms if left alone.

Whether screening mammograms can lower women's risk of women dying from breast cancer has been debated for decades, and this latest study reignited a fury of reactions on both sides.

Breast surgeon Dr. Mette Kalager, former director of the Norwegian Breast Screening Program, left her position a decade ago because of doubts about the value of screening and reluctance to spearhead a program that she would not participate in herself.

The U.S. Position on Mammograms

American Cancer Society guidelines recommend that women 45 to 54 should get mammograms every year, those 55 and older should get them every other year, and women 40-44 should have the option of screening or not. The U.S. Preventive Services Task Force (2009) recommended against the use of routine mammography screening for women under 50 and recommended that women 50 to 75 get screened every two years. The Task Force concluded that for women 40 to 49 the benefits of mammograms do not outweigh the harms, including false-positive results that lead to unneeded breast biopsies and follow up-imaging, and to unnecessary anxiety and distress. Also, the Task Force found that mammograms play an “extremely modest role in reducing the likelihood of dying from breast cancer.”

Dr. Otis Brawley of the American Cancer Society noted that at least eight prospective randomized trials, in which women were randomly assigned to screening or no screening, have shown that screening saves lives, but he admitted that at least a dozen studies have shown that screening mammograms do lead to overdiagnosis of breast cancer in 15% to 50% of cases, a phenomenon he called for doctors to accept. Elaine Schattner, Forbes columnist, called that “overdiagnosis awareness.” In my mind, “overdiagnosis awareness,” like “breast cancer awareness,” is just a small step towards solving a big problem. In fact, five problems:

Problems with Breast Cancer Overdiagnosis

  • Overdiagnosis leads to overtreatment, which can cause morbidity and mortality. Overdiagnosis of breast cancer often leads to surgery, chemotherapy and radiation, treatments that could harm women without providing any benefit, since their tumors would never have made them sick. Ductal Carcinoma in Situ (DCIS), for example, also known as “stage 0,” is not really cancer. According to the American Cancer Society, a diagnosis of DCIS means the cells that line the milk ducts of the breast are abnormal and look like cancer cells under a microscope, but they are non-invasive and have not spread into surrounding breast tissue. Barry Kramer, M.D., Director of the National Cancer Institute’s Division of Cancer Prevention, noted that treatments for DCIS are associated with potential harm, stating “exposure to radiation therapy increases the risk of developing secondary cancers in the future, and mastectomy can cause serious health problems as well.”  
  • Overdiagnosis is crazy-making. It could be enough to give you cancer. I’ve written plenty about stress and cancer, including its ability to imbalance hormones, suppress your immune system, compromise digestion and nutrient absorption, interfere with sleep, suppress healing, and lead to health-eroding habits like smoking or drinking, among other outcomes.  
  • Mammographic screening can cause breast cancer. Well that’s a biggie! According to the American Cancer Society, women who as children or young adults were treated with radiation therapy to the chest for another cancer (such as Hodgkin disease or non-Hodgkin lymphoma) have a significantly higher risk for breast cancer. The risk of developing breast cancer from chest radiation is highest if you had radiation during adolescence, when your breasts were still developing. Although many experts believe that the low-dose exposures to radiation received as a result of mammography procedures are not sufficient to increase risk for breast cancer, recent evidence indicates that the lower-energy X-rays provided by mammography result in substantially greater damage to DNA than expected and that risk of breast cancer caused by exposure to mammography radiation may be greatly underestimated (Heyes, 2009). It is often recommended that high-risk women, including those with BRCA mutations, begin annual mammography screening as early as age 25. Research now demonstrates that young women with the very genetic mutations that lead them to begin mammography screenings at earlier ages are actually more vulnerable to the cancer-inducing effects of early and repeated exposures to mammograms. A 2012 study found that diagnostic radiation exposure before age 30 increased risk of breast cancer in a dose-dependent manner among women with genetic mutations.  
  • There are alternatives to mammograms. This is not about NOT screening. There are other non-invasive screening tests -- often earlier, safer and more sensitive -- like ultrasound, MRI, and thermography. These are especially useful for dense breasts, a characteristic that has been linked to a slightly higher risk of breast cancer as well as increased difficulty in seeing tumors on mammograms. As Elaine Schattner wrote for Forbes, “breast ultrasound is crucial for detecting tumors in premenopausal and some older women who have dense breasts.” 
  • Screening and early detection are not true prevention – lifestyle factors like diet, alcohol consumption, xenoestrogen exposure, exercise, and stress seem to be key. Cohort studies (forward-looking prospective research studies that investigate the causes of disease, establishing links between risk factors and health outcomes) are already pointing in those directions. That prevention-oriented research needs to be expanded, and women need to learn how to apply what has already been published in their daily lives. In the latter regard, we at BeatCancer.org are certainly doing our part.
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    References:

    [1] Heyes, G., Mill, A., & Charles, M. (2009). Mammography: oncogenecity at low doses. J Radiol Protect, 29, 123–132.

    [2] http://www.breastcancerfund.org/clear-science/radiation-chemicals-and-breast-cancer/ionizing-radiation.html?referrer=https://www.google.com/

    [3] http://www.cancer.org/cancer/breastcancer/detailedguide/breast-cancer-risk-factors

    [4] http://www.cancer.org/cancer/breastcancer/detailedguide/breast-cancer-treating-ductal-carcinoma-in-situ

    [5] https://www.cancer.gov/news-events/cancer-currents-blog/2015/dcis-low-risk

    [6] Jørgensen KJ and Gøtzsche PC. Breast cancer screening in Denmark: A cohort study of tumor size and overdiagnosis. Annals of Internal Medicine, Jan 10, 2017. http://annals.org/aim/article/2596394/breast-cancer-screening-denmark-cohort-study-tumor-size-overdiagnosis

    [7] Pijpe A, Nadine Andrieu N, Douglas F Easton DF et al. Exposure to diagnostic radiation and risk of breast cancer among carriers of BRCA1/2 mutations: retrospective cohort study. BMJ 2012; 345. 06 September 2012. http://www.bmj.com/content/345/bmj.e5660

    [8] Rubin R. Do screening mammograms cut breast cancer deaths or lead to overtreatment? Probably both. Forbes, Jan. 10, 2017. http://www.forbes.com/sites/ritarubin/2017/01/10/do-screening-mammograms-cut-breast-cancer-deaths-or-lead-to-overtreatment-probably-both/?bblinkid=35871417&bbemailid=3021017&bbejrid=210626828#25aa454af126

    [9] Schattner E. The latest study on breast cancer overdiagnosis fails to persuade. Forbes, Jan. 10, 2017. http://www.forbes.com/sites/elaineschattner/2017/01/10/the-latest-study-on-breast-cancer-overdiagnosis-fails-to-persuade/?bblinkid=35871418&bbemailid=3021017&bbejrid=210626828#a3f08111c44b

 

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