The issue seemed to have been settled: According to the latest expert guidelines from the Centers for Disease Control (CDC) and the United States Preventive Services Task Force (USPSTF), women who do not have clear risk factors for breast cancer–such as a family history of breast cancer in a first-degree relative–should have their first screening mammogram at age 50, and should continue having mammograms every other year until age 74. The facts were compelling; only in this age group could investigators demonstrate any benefit–and even here, the benefit was small–in reducing the number of deaths from breast cancer.
New Study Casts Doubt on Current Screening Guidelines
However, a new study has once again inflamed the controversy surrounding the right time to start breast cancer screening. In this report, researchers went back and looked at more than 600 women who had died of breast cancer and found that approximately 70 percent of the deaths had occurred in women who didn’t have mammograms, and half of those who died were under age 50. Sounds like a compelling case to begin mammography at an earlier age–say, 40–doesn’t it?
The answer is probably no. Here’s why:
- The study was a retrospective (backward-looking) “failure analysis.” Such studies cannot prove that a particular test or treatment causes a benefit; they can only be used to identify a possible connection between one thing (e.g., delaying mammograms until age 50) and another thing (e.g., dying of breast cancer.).
- Unfortunately, the study was flawed because it examined only women who died of breast cancer. The analysis didn’t include a control or reference group of women who survived breast cancer. Without knowing the percentage of survivors who didn’t get mammograms, it’s impossible to even begin to determine whether mammograms can make any difference in preventing deaths due to breast cancer.
- Cancers that cause death in women younger than age 50 tend to be very fast-growing, and finding these cancers earlier might make no difference in the ultimate outcome. Catching and treating these cancers later, when they begin to cause symptoms, may yield the same results as those caught and treated earlier. Early detection does not necessarily result in better outcomes for patients.
- Screening also has many drawbacks. Mammography often detects tumors that turn out to be benign or so slow-growing that they are harmless and require no treatment. Unfortunately, identifying such tumors will often trigger cascades of further tests and treatments, sometimes culminating in surgery and even chemotherapy, with risk of harm at every step, all to combat something that, if left alone, would never have caused a problem. In addition, all this testing and treatment can cause anxiety that, as recent studies have shown, can persist for many years. High-quality research has shown that thousands of women would have to be screened to prevent one breast cancer death, whereas hundreds of those women would face serious psychological distress, uncertainty, and even physical harm.
The study analysis is thus deeply flawed, primarily because it doesn’t address, and cannot address, the two most fundamental questions: (1) does the benefit of early screening outweigh the risks, and (2) will earlier screening save lives?
If, when the uproar subsides, the leading experts in the field decide to re-examine the data that led to the current guidelines and revise their recommendations, we will publish an update on this topic. In the meantime, we’ll continue to keep an open mind to new information that can help you receive the very best medical care and achieve all of your health goals.
The One Medical blog is published by One Medical, an innovative primary care practice with offices in Boston, Chicago, Los Angeles, New York, Phoenix, the San Francisco Bay Area, Seattle, and Washington, DC.
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