How Many Lives do Mammograms Actually Save?
The answer seems to be ‘very few.’ Women must be given accurate information outlining the risks and benefits of mammography so that they can make an informed decision about whether to be screened.
Several studies have reported decreasing breast cancer mortality rates as a means of justifying the use of routine mammograms. However, the benefits of mammograms are exaggerated by the medical profession. The data is not entirely accurate for a number of reasons.
Over the first thirty years of widespread routine mammography, deaths from breast cancer decreased by 28% in the U.S. in women over 40; but how much of this decrease was actually due to screening? Probably very little. It is worth noting that the decrease in breast cancer mortality during the same time period in women who have not had mammography (those under age 40) was even greater (42%), implying that reduced smoking, less use of estrogen, dietary improvements and possibly improved treatment methods, rather than screening, are primarily driving decreased mortality.1
One major problem with mammograms is overdiagnosis. First of all, eighty percent of biopsies initiated by a mammogram result are negative. Also, mammograms are quite sensitive, but do not distinguish between low-risk and high-risk tumors. This means that many slow-growing, non-threatening tumors are being detected and treated unnecessarily. 2, 3 Overdiagnosis also means that many women who believe that their lives were saved by a mammogram were not saved — they were actually harmed, treated unnecessarily for a cancer that would have never put their life in any danger. The number of women “overdiagnosed” has been estimated at 70,000 per year, or 20-30% of diagnosed breast cancers.1
Unnecessary treatments have serious consequences. Studies that report decreased breast cancer mortality rates due to mammograms fail to report all-cause mortality, and should be ignored; unnecessary treatments may increase the risk of death from other causes. For example, radiation therapy has been found to increase the risk of other cancers.4 Chemotherapy may lead to neuropathy, premature menopause, osteoporosis, and of course congestive heart failure and other cancers resulting in increasing other causes of death.5 When breast cancer treatment causes death by other causes it looks like a success, as it reduces breast cancer mortality.
In women under the age of 50, false positive results are very common.3 Plus, false positive tests mean additional mammograms — more exposure to radiation. The cumulative radiation effects of yearly mammograms starting at age 40 on breast cancer risk is still unclear, but should not be dismissed.
Many dangerous and aggressive cancers cannot be detected by regular mammograms because they can grow rapidly and become lethal in the time interval between screenings — meaning that mammograms cannot prevent these cancers from advancing to late-stage.2, 3 Over the past thirty years, the number of early stage breast cancers has skyrocketed, the number of late-stage cancers has decreased only very slightly, and the number of cases of life-threatening metastatic cancer has not changed. This information implies that early detection is not preventing advanced, invasive tumors.1
Another issue with mammograms is lead-time bias, which inflates survival data and misleads women. Even if the early diagnosis doesn’t change a woman’s time of death, her survival is seemingly longer because she was aware of the cancer earlier. It makes it look like mammograms were extending women’s lives because they are living longer with the cancer diagnosis.
We may not be able to exactly ascertain how much benefit mammograms provide, but if there is one, it is going to be a tiny amount.The most careful analysis of the data we have shows that we should direct our efforts toward prevention, not early detection. The pink ribbon campaigns are misguided and their main purpose is to promote mammograms, which is actually emphasizing the wrong approach to save lives. We need to focus on advances in nutritional science instead.
The Nordic Cochrane Centre, an independent research group that conducts extensive and thorough reviews of the medical literature, assessed the potential benefits and harms of mammography in 2009. These were their conclusions: For every 2000 women that are screened regularly for ten years, one will have her life prolonged. However, 10 healthy women will be unnecessarily treated for breast cancer, either by having a lumpectomy, mastectomy, chemotherapy, or radiotherapy. Also, 200 healthy women will experience a false alarm, leading to substantial psychological and emotional strain. In their analysis, the Cochrane group stated that it is “not clear whether screening does more good than harm.”6 A pamphlet on the potential harms and benefits of mammography screening is available on the Cochrane group’s website. In 2009, the U.S. Preventive Services Task Force began recommending against routine screening mammography in women between the ages of 40 and 49.7 The promotion and use of mammograms also have our female population living in fear and under stress and that is not emotionally healthy and also threatens healthy life expectancy.
Whether or not to undergo mammography is a personal choice, but it is important to know the true risks and benefits of the screening in order to make a sound decision. Regardless of their decision on this matter, women should not rely on detection by mammography to protect them against breast cancer. The take home message is that mammograms can’t be counted on as the sole intervention to save women’s lives — they do very little to extend lifespan of women. To save millions of years of life, we must take steps to prevent breast cancer from developing in the first place — for example, exercising regularly, maintaining a slim, healthy weight, eating plenty of mushrooms, onions, and cruciferous vegetables, using flax or chia seeds daily, minimizing processed foods and animal products, maintaining adequate vitamin D levels, and limiting alcohol consumption — is a much more effective approach than detecting and treating breast cancer after it has begun to develop. If our population promoted the benefits of a nutritarian diet to protect against breast cancer, millions of lives would be saved from breast cancer and other common life-threatening diseases. In our own lives, we must focus our efforts on where we can do the most good: prevention via lifestyle measures, not early detection.
1. Bleyer A, Welch HG: Effect of three decades of screening mammography on breast-cancer incidence. N Engl J Med 2012, 367:1998-2005.
2. Esserman L, Shieh Y, Thompson I: Rethinking Screening for Breast Cancer and Prostate Cancer. JAMA: The Journal of the American Medical Association 2009, 302:1685-1692.
3. Wright CJ, Mueller CB: Screening mammography and public health policy: the need for perspective. Lancet 1995, 346:29-32.
4. Armstrong K, Moye E, Williams S, et al: Screening mammography in women 40 to 49 years of age: a systematic review for the American College of Physicians. Ann Intern Med 2007, 146:516-526.
5. Rock E, DeMichele A: Nutritional approaches to late toxicities of adjuvant chemotherapy in breast cancer survivors. J Nutr 2003, 133:3785S-3793S.
6. Gotzsche PC, Nielsen M: Screening for breast cancer with mammography. Cochrane Database Syst Rev 2009:CD001877.
7. Screening for breast cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med 2009, 151:716-726, W-236.