According to a recent study published in the New England Journal of Medicine, mammograms have overdiagnosed 1.3 million American women with breast cancer over the last 30 years. Of these 1.3 million women, most opted for invasive treatments—surgeries such as lumpectomies and double mastectomies, and drugs such as chemotherapy, radiation, and hormonal therapies…and most of these women had abnormalities that would never have harmed them.
The benefits of breast cancer screening with mammograms must be weighed against the dangers of overdiagnosis. A separate 2013 study revealed that radiation treatments for breast cancer increase the risk of developing lung cancer, and other studies have shown that chemotherapy may harm the heart. The drug tamoxifen has been shown to double your risk for endometrial cancer. It’s saved the lives of many women who did indeed need it, but for the women diagnosed with a harmless form of breast cancer that would never have claimed their lives or even shown symptoms, the treatment isn’t a worthwhile tradeoff.
Without a doubt mammograms save lives, but for every life saved, even more are put at risk. In a 2013 report published in the medical journal BMJ, breast surgeon Michael Baum estimates that for every breast cancer death averted via mammogram, there are 1-3 future deaths that can be linked to the side effects of breast cancer treatments.
Just How Effective Are Mammograms
The mammogram debate has been ongoing for the last 25 years, ever since the National Cancer Institute stopped recommending that women in their forties get screened for breast cancer with a mammogram. There just wasn’t enough evidence to suggest that mammograms were effective at preventing breast cancer deaths.
In 2014, an analysis of two landmark Canadian studies that followed nearly 90,000 women over 25 years revealed that mammograms didn’t decrease breast cancer deaths whatsoever. An American study that same year showed that higher rates of mammogram screenings led to more breast cancer diagnoses, but did not reduce breast cancer deaths overall.
Over the last 3 decades, rates of breast cancer deaths have fallen significantly: by 28% in women 40 years and older and by 42% in women younger than 40, although most of these women never got screened. The decrease in breast cancer rates can’t be attributed to mammograms. According to the New England Journal of Medicine we can thank advancements in new medicines like tamoxifen and targeted chemotherapy and radiation for the decrease in breast cancer deaths.
How Breast Cancer Really Works
Cancer that is lethal metastisizes, or spreads to other parts of the body. But more often than not, what’s caught on a mammogram, or even on the subsequent biopsy, is a type of cancer or abnormality that isn’t harmful and will never spread. Unfortunately, we don’t have the means to differentiate between what’s deadly and what’s harmless, and many doctors recommend drastic measures such as mastectomies, regardless of the abnormality.
Mammograms make sense when it comes to catching tumors that grow gradually and eventually spread to other areas of the body. Scientific evidence, however, suggests that breast cancer doesn’t work in such a linear (and controllable) manner.
Mammograms work great at catching the type of cancer that can jump to other parts of the body but can be stopped if caught early enough. Unfortunately, less than 30% of breast cancer cases happen to be this type of cancer. More often they are the type of cancer to move so slowly that they will never cause harm and you will never need treatment…or they are the type of cancer that is so deadly there is no stopping it, because it has sent cancer cells throughout the body before it can ever be detected.
Ductal carcinoma in situ, or DCIS, is an example of an abnormality that accounts for 20- 30% of breast cancer diagnoses, but many experts consider DCIS not to be cancer at all, but precancer.
Duke University breast surgeon Shelley Hwang shared with Elle magazine the “terrible feeling” that overcomes her every time she’s asked to perform an elective double mastectomy on a woman with DCIS who “almost certainly” would have lived a long life without the procedure.
Getting a mammogram is a personal choice, one that should be weighed according to your family and individual medical history. To help you with that decision the National Cancer Institute provides a free risk calculator at their website, and the Breast Cancer Surveillance Consortium offers an app that also figures your breast density into the equation.