Should You Get a Mammogram?

Should You Get a Mammogram?

It’s worth keeping in mind that screening for breast cancer does carry some risks.

In February 2014, the prestigious British Medical Journal (BMJ) published a study suggesting that mammograms are ineffective at saving lives. It wasn’t the first time this had been suggested by the medical community—though the finding contrasted with many previous studies. So, what was different about the BMJ research that made headlines across the country? And what does it mean for women considering a mammogram?

The BMJ study was large, with almost 90,000 women followed for 22 years. It compared women getting mammograms (an X-ray of the breast) to women getting physical exams of their breasts by a doctor. Almost 1,200 women were diagnosed with breast cancer during the study, almost exactly the same in each group. The large number of cancers, and particularly the long duration of follow-up, made it possible for the researchers to do a more thorough analysis than previous studies.

Understanding breast cancer
Before I go further into what the study showed, it is important to note that breast cancer is not a single diagnosis. There are several types of breast cancer, and even the invasive type that the BMJ study focused on can vary among women. Some breast cancers are very aggressive, spreading quickly to lymph nodes and organs; others are more slow-growing. Some breast cancers are so slow-growing that they don’t need to be treated.

Unfortunately, right now it’s impossible to know exactly how aggressive the cancer will be, so we treat all invasive breast cancers the best we can. That may mean surgery, radiation and/or chemotherapy. We know that some women have been treated unnecessarily, but the belief among cancer doctors has been this: By treating all breast cancers found on screening, we are saving some lives, even if we are treating some women who aren’t getting benefit from treatment.

In reality, only cancers that grow at just the right speed can be cured by a screening program. They need to be slow enough that they can be treated before spreading, and not so slow that they will never bother the patient.

Mammogram risks
The authors found that there was no significant difference in breast cancer deaths in the mammogram group compared with the physical exam group. But is there actual harm in getting a mammogram?

The BMJ study showed that more than 20 percent of breast cancers found on mammography, all of which were treated, were “overdiagnosed”—destined never to cause death. One problem with treating these types of cancers is that some chemotherapy and radiation can cause health problems, such as an increase in heart disease and other types of cancer.

Not the last word
What does this mean for women now? I don’t think this is the last word on mammograms. A number of scientific concerns were raised about the study. One is that the quality of mammograms used in the study was not as good as the current technology. Another is that the study did not evaluate high-risk women, such as those with BRCA mutation or strong family history.

Given that, I believe that some women will be cured of breast cancer with a mammogram who won’t be cured without it. However, that number is smaller than we thought it was. Also, more women will be treated unnecessarily than we thought—and that might be about one in every 400 or so women who undergo screening.

The decision still belongs to a woman and her doctor. For those who want every chance of reducing death from breast cancer, I believe a mammogram is still of some modest benefit, but it needs to be balanced against the anxiety of a false positive test (not addressed in this study) and the possibility of unnecessary treatment. For women who have been reluctant to get mammograms, there is now enough doubt that I wouldn’t try to talk a woman into getting one.

Medically reviewed in October 2019.

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