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Risks and Benefits of Mammograms

What are the benefits and harms of breast cancer screening using mammograms?  Why are breast cancer screening recommendations conflicting amongst various expert groups in the recent years?  Let's find out what the controversy is all about.

By
Sanaz Majd, MD,
October 20, 2016
Episode #200

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The American Cancer Society (ACS) changed its recommendations regarding breast cancer screening last year. I know what you are thinking: again? How many expert groups keep changing their screening mammamography recommendations, and why are all of them seemingly conflicting? Why can’t the medical community come to a consensus on this important issue?

I recently discussed the controversy surrounding breast cancer gene testing, and what to consider before you get tested. Breast cancer screening is now such a hot topic that I couldn’t pass up the opportunity to answer some of the most common and controversial questions I receive from my patients stemming around breast cancer screenings: When should you start?  How often should you get screened? When should you stop? In order to help interpret these conflicting and rather mysterious expert group recommendations, it's important to first learn the true harms and benefits women should consider when we make these vital and individualized decisions.

Potential Mammogram Risks

Breast cancer is the #1 cancer diagnosed in women. It’s also the second cancer that causes death in women in the U.S.  The great news is that, as medical treatment has advanced in this area, the rate of breast cancer mortality has declined since 1990, and the overall incidence of this cancer has stabilized since the year 2000—very quite possibly secondary to diminished use of hormonal replacement therapy in post-menopausal women since the landmark study from Women’s Health Initiative (WHI) around the same time.

Some of you may be wondering why anyone would decide against a test that can possibly aid in the diagnosis of any cancer, right? Well, the truth is that every test has its own pros and cons, and these pros and cons are weighed against each other in research studies and discussed amongst expert groups in detail, and medical guidelines are then created after this process.  Like we learned about the breast cancer gene controversy, some tests, especially those concerning the word “cancer,” can actually have potential harm. Here are some of the reported mammogram cons:

1.  False-Positives: Approximately 10% of routine screening mammograms recommend further evaluation. This would mean that the patient would be asked to return for more mammogram views, ultrasounds, or even a breast biopsy. And over 90% of these cases turn out benign and non-cancerous. These false-positives are more common in younger women, since the mammogram is not as good at detection due to greater density of the breasts on imaging that can obscure a small cancer, and because breast cancer tends to be less common in younger women.

2.  Overdiagnosis:  Some cancers are slow-growing, and if you left them alone, they may never progress and cause problems or death. Studies show generally anywhere between less than 10 to 30% of breast cancers may actually be overdiagnosed. 

3.  Radiation Exposure:  A few studies show that ionizing radiation can cause breast cancer. However, these studies used higher-dose radiation than what the typical mammogram uses, thereby over-estimating the results.  According to the US Preventive Services Task Force (an expert group that sets many guidelines for doctors), approximately 16 out of 100,000 women who obtain an annual mammogram over a lifetime can possibly attribute the cancer to ionizing radiation.  The risk is so low, and the risk of breast cancer in women much higher, so that screening initiation at age 40 has been shown to have outweighed benefits than any small risk due to radiation.

4. Psychological Stress:  Imagine hearing word that your mammogram is “suspicious” for cancer. How would you feel? How many restless nights would that cause?  And how would that change your outlook on screenings later? Studies show that women feel the aftermath of false-positive readings, sometimes for months after the event. False-positive mammograms can cause significant anxiety and many sleepless nights for some women who fear they have cancer after an abnormal mammogram. This psychological stress is not for the light-hearted.

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