by Laura Manns-James, PhD, CNM, WHNP-BC
As you may have gathered from the title, this isn’t going to be a typical breast cancer awareness month post with lots of advocacy for mammography and self-breast exams. American women are already fearful of breast cancer, having received 30 years of public health messaging on the importance of early detection. We’re aware, already! We’ve been told by mammography campaigns that we are selfish or even crazy if we put off being screened, and pink ribbons abound in our everyday lives, adorning everything from cars to bathroom stalls (*Resource 1). But is all this screening and early detection really working? If we really want to “save the ta-tas”, what’s the best way to go about it?
The answer to this question is somewhat complicated, so bear with me. While the number of breast cancer diagnoses has risen since 1990, the number of breast cancer deaths has gone down. At first, it seemed reasonable to believe that the reduction in death rates was due to screening effectiveness: more women were getting mammograms, and deaths were going down, so surely screening was working! Breast cancers were being detected earlier, allowing for earlier treatment, preventing more breast cancer deaths. Makes sense, right? But growing evidence now suggests something else was really responsible for the reduction in breast cancer deaths: better treatment. Treatment was improving to the point that no matter when a breast cancer was discovered—earlier or later in the disease process—fewer women were dying of it.
While the idea that early detection saves lives makes a lot of sense intuitively, more and more evidence is suggesting that it just isn’t so. We don’t actually see a decrease in breast cancer deaths when women who are at low or average risk do formal monthly self-breast examinations. Nor do we see any differences with screening clinical breast exams performed by doctors or advanced practice nurses (*Resource 2). These findings about self-breast exams are based on studies that include hundreds of thousands of women, so the evidence that these screening methods don’t work is quite strong.
More recent evidence suggests that even mammography doesn’t actually save lives; while it may prevent a few more women from dying of breast cancer each year (about 2 or 3 in 1000), there are more deaths from other causes in the group of women that regularly engage in mammography screening — so the overall death rates are about the same, whether women get mammograms or not (*Resource 3). Mammography means slightly fewer deaths from breast cancer, and slightly more deaths from other causes, at the same ages.
So why doesn’t screening work better? After all, it seems like it should, right? It turns out that screening “works”— in the sense that it makes a difference between life and death for women with breast cancer — in a surprisingly small number of situations. Some breast cancers grow very, very slowly—and provide plenty of time for intervention no matter how the cancer is found. Other cancers (thankfully few in number!) are so aggressive that finding them early doesn’t really matter, because no available treatments work (*Resource 4). So it’s the medium-speed cancers that screening is designed to address. But even medium-speed cancers are treatable with chemotherapeutics and interventional radiology these days, and early detection just isn’t as important as it was in the days before these treatments improved.
But what’s wrong with breast cancer screening, if it reassures us? Even if it doesn’t actually save our lives, isn’t there value in finding out on a regular basis that no disease is lurking in our breasts? Well, this brings us to the downside of screening: unreliable results. It turns out that formal monthly self-breast examination, clinical breast exams by a physician or advanced-practice nurse, and mammography frequently find problems that aren’t really there. In fact, somewhere between 91 and 98% of all abnormal screening mammogram results for women ages 40 to 70 are false positives: they don’t turn out to be cancer. These abnormal results also occur frequently: 50% of women who have annual screening mammograms will experience an abnormal result in a 10-year period (*Resource 5). After an abnormal screening mammogram, we have to sort out what’s really happening….and that means a woman has to wait nervously while additional tests are performed. Sometimes that means an ultrasound or MRI, and sometimes that means a biopsy. Either way, it’s usually days to weeks before she knows whether or not she cancer. That’s a long time to be in limbo, and abnormal mammograms cause a lot of anxiety (*Resource 5).
Sometimes even with the additional testing, a woman still won’t know whether or not she really has invasive cancer. Mammograms are so good at finding tiny clusters of concerning-looking cells that they are now identifying a whole category of maybe-cancers: cells that look like they could become invasive cancer, but haven’t yet. These ductal carcinomas in situ, which make up 1/5 of new breast cancer diagnoses, (*Resource 6) are typically treated rather than observed–which means about 15 in 1000 screened women are getting treatment for abnormal cells that might, if left alone, never actually become invasive and harm them (*Resource 3).
Currently, the U.S. Preventive Services Task Force recommends screening mammography starting at age 50 for low and average-risk women, to be repeated every two years. They do not recommend clinical breast exams or formal self-breast examination. Women have the right to understand the benefits and the risks of screening, and conversations with clinicians should provide an overview of their options, not just an appointment for mammography. It should be noted that some groups of women are at very high risk for developing breast cancer, and they may benefit from mammography and/or preventive surgery. Women with heritable BRCA-1 and-2 mutations are at very high risk for developing breast cancer, as are women who have a history of chest radiation — particularly as young adults or children (*Resource 7). These women should talk with breast specialists about an individualized plan of screening and prevention. While disparities in breast cancer deaths persist among women of different ethnic and racial groups (*Resource 8), screening recommendations don’t change based on ethnicity.
If screening for most women isn’t all it’s cracked up to be, what can we do to prevent breast cancer? Fortunately, there are some things we can do to reduce our risk (*Resource 9): first, maintain a healthy weight and normal body mass index. Obesity increases breast cancer risk. Second, reduce or avoid alcohol consumption. Alcohol helps breast cancers develop. Third, breastfeed as long as possible. Breastfeeding reduces the risk of breast cancer considerably, and the longer we nurse, the better. These steps actually reduce the risk of developing breast cancer in the first place.
Finally, while we no longer recommend monthly self-breast examination–since the extra time doesn’t really make a difference, and women only have so much time and energy–it’s true that women still often find their own breast cancers in the course of daily events. Anything a woman notices in her breasts that’s different for her should be brought to the attention of her clinician to be evaluated. Then we aren’t using these tests for screening, we’re using them for diagnosis–and their benefit-to-risk balance improves.
For more information and a handy video about the benefits and risks of breast cancer screening, let Dr. Gilbert Welch explain:
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- Kosters JP, Gotzsche PC. Regular self-examination or clinical examination for early detection of breast cancer. The Cochrane database of systematic reviews. 2003(2):Cd003373.
- Loberg M, Lousdal ML, Bretthauer M, Kalager M. Benefits and harms of mammography screening. Breast Cancer Res. 2015;17:63.
- Welch HG, Prorok PC, O’Malley AJ, Kramer BS. Breast-Cancer Tumor Size, Overdiagnosis, and Mammography Screening Effectiveness. N Engl J Med. 2016;375(15):1438-1447.
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- Evans A, Vinnicombe S. Overdiagnosis in breast imaging. Breast (Edinburgh, Scotland). 2017;31:270-273.
- Derman YE. Clinical Practice Recommendations Based on an Updated Review of Breast Cancer Risk Among Women Treated for Childhood Cancer. J Pediatr Oncol Nurs. 2017:1043454217727515.
- Centers for Disease Control and Prevention (2016, June 15). Breast Cancer Rates by Race and Ethnicity. Retrieved September 27, 2017, from https://www.cdc.gov/cancer/breast/statistics/race.htm
- PDQ Screening, Prevention Editorial Board. Breast Cancer Prevention (PDQ(R)): Patient Version. In: PDQ Cancer Information Summaries. Bethesda (MD): National Cancer Institute (US); 2002.