Agency for Healthcare Research and Quality Urge Improved Screening
Now isn’t that better? Let’s get the focus right. The US Department of Health & Human Services’ recent study results do not urge women to abandon mammograms or to stop self-breast exams. Rather, it recommends development of new and improved methods, so we can better diagnose breast cancer and thus avoid unnecessary surgery, treatment, and anxiety. So while the popular press is getting everyone up in arms about the government trying to take our mammography away, and congress is reassuring us that won’t happen, the real message is lost in the frenzy.
I first read about the Breast Cancer Screening study November 18, in the Washington Post. The Post suggested that women didn’t need to have mammograms until after 50, then only every two years; that women over 74 didn’t need them at all; that doctors stop performing breast exams in the office and to abandon teaching women how to do self-breast exams. One in 8 women will be diagnosed with breast cancer sometime in their life, one in thirty will die from breast cancer. The older we get, the more likely we are to be diagnosed with breast cancer. With these odds, my response was “What are we supposed to do then? Just wait until we notice a lump in the mirror?” I felt compelled to look up the actual study, so I went to the Agency for Healthcare Research and Quality website, We should be applauding the US Preventive Service Task Force (USPSTF) for commissioning the study, rather than wringing our hands in dismay.
First a little background into the scientific method, which we all learned about in grade-school. Most of us are no longer as smart as a fifth-grader, or at least we can use a little “oh, yeah, I remember that…”
Start with propose the hypothesis, design a study, analyze the results, and come to conclusions. Simple as this may sound, things often go awry. The study must be designed to answer the question posed in the hypothesis, and the conclusions must be related to the questions asked. In it’s purest form, the conclusion states whether or not the hypothesis is correct or not.
The goal was to look at statistics from existing studies to determine just how effective breast cancer screening is. USPSTF posed these questions:
Does mammography reduce the breast cancer mortality rates among women over a broad range of ages when compared with usual care? If so, does mammography reduce breast cancer mortality rates among women 40 to 49 years of age when compared with usual care?
USPSTF reviewed 154 publications and took data from 8 different randomized trials of screening mammography ad two trials of breast self-examination (BSE). Close to 600,000 women were followed for 11-18 years in these 8 studies.
USPSTF reported on the Sensitivity, Specificity, and Effectiveness of mammography, as well as adverse effects.
Sensitivity: Of the women in the studies diagnosed with breast cancer, 70% to 96% were detected by mammography. The sensitivity was lower with women in their 40s than for older women. Population statistics tell us what happens with women as a whole, but cannot be applied to individuals. There are many variables that can effect a woman’s chance of an accurate diagnosis: hormone therapy, breast density, experience of the radiologist, etc.
Specificity: The older the woman gets the more likely a positive mammography is actually cancer. For women in their 40s only 1-4% positive mammograms will be cancer; for women in their 50s, 4-9%; for women in their 60s, 10-19%; and for women in their 70s, 18-20%.
Effectiveness: For women getting mammograms at age 40-49, about 1400 women must be screened for 14 years in order to save one woman from dying of breast cancer. Women 50 years or older, one death can be prevented by screening about 840 women for 14 years. The effectiveness did not change when combined with a breast exam in the doctor’s office, or with self-breast exams.
Adverse effects: Most women in the study expressed discomfort, anxiety and concern about associated positives mammograms and follow up tests. Almost all of the women (99%) knew that there is a potential of a false positive result, however most did not understand how likely that was. Still, 2/3 of the women were willing to undergo 500 false positive test results if it meant saving one life.
Most women (94%) are unaware that a non-progressive form of cancer, ducal carcinoma in situ, or DCIS, is diagnosed with mammograms. Most of these cancers are not life-threatening, yet 67% are treated with radiation, lumpectomy, or mastectomy. There is a chance that the radiation from mammograms may actually induce cancer. For 100,000 women getting mammograms from age 40 on, there may be up to 8 deaths induced by the radiation.
The risk of false positives and the consequences decreases with age. The balance between increasing risk and decreasing harms is more favorable over time. Women over 70 have a higher risk of cancer, and also a higher incidence of DCIS, which is not life threatening. Women over 70 statistically are more likely to be suffering from other diseases that shorten their life, and less tolerant of aggressive cancer treatments. Doctors’ exams and self-exam did not reduce the chances of dying from breast cancer.
Contrary to what the press reports, the study does not recommend abandoning any of the current methods of detecting breast cancer.
The recommendations are so important that I will quote them from the report:
Future research should be directed toward developing new screening methods as well as methods of improving the sensitivity and specificity of mammography. Methods of reducing surgical biopsy rates and complications of treatment should also be studied, as should communication of the risks and benefits associated with screening to patients. Finally, efforts to identify breast cancer risk factors with high attributable risk, as well as appropriate prevention strategies, should continue. Even in the best screening settings, most deaths from breast cancer are not currently prevented.
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