Screening Mammography: Saving Lives Or Overdiagnosis Overkill?
By Lissa Rankin on May 21, 2013
In response to last week’s blog post Was Angelina Jolie “Medically Hexed?” many of you wrote to me asking my medical opinion on screening mammography. So… gulp… here we go. You asked. Mind you, this is simply my understanding of the very complex data – and this blog post is all about my personal opinion and how I came to it – but I totally respect your right to have a very different one! If you or someone you love has had your life saved as the result of mammography, I’m so glad this technology has helped you. My father was a radiologist specializing in mammography, and he’d probably roll over in his grave if he read what I’m about to write. But as I said, this is just my humble opinion. Because you asked.
Like genetic testing for things like the BRCA gene, screening for breast cancer is not a black and white issue, so I can’t give you a simple “Thumbs up” or “Thumbs down” on whether I think all women should or shouldn’t be getting mammograms. Like many medical decisions, it’s very personal, and each woman has to choose for herself what is right, based on her family history, her threshold for risk-taking, her tendency to fear the unknown, and her analysis of the data that shows that while early screening may save lives, it also leads to a great deal of what researchers call “overdiagnosis” and “overtreatment.”
Keep in mind that what I’m about to talk about is screening mammography, not diagnostic mammography. Screening mammograms are performed when there’s no breast lump or other worrisome breast abnormality, while diagnostic mammograms are performed when there is a known breast abnormality, such as a lump or an abnormal screening mammogram.
I’m also not talking about women with strong family histories or known BRCA gene status. For those women, I strongly recommend regular mammography and follow up with biopsies when necessary.
As you’ll be able to tell if you read old blog posts of mine, I was always pro-mammogram until I started researching the book I’m currently writing The Fear Cure: Cultivating Courage As Medicine For The Body, Mind & Soul (the sequel to Mind Over Medicine: Scientific Proof That You Can Heal Yourself.) In my research, I’ve uncovered shocking data about breast cancer screening that I’ll share with you in this post.
Overdiagnosis Of Cancer
A study published in the Journal of the National Cancer Institute estimates that 25% of breast cancers detected on mammogram, 50% of lung cancers diagnosed by chest X-ray and sputum analysis, and 60% of prostate cancers diagnosed by prostate specific antigen (PSA) are “overdiagnosed.” The study also evaluated overdiagnosis of neuroblastoma, thyroid cancer, melanoma, and kidney cancer.
The authors of the study define “overdiagnosis” as “the diagnosis of a ‘cancer’ that would otherwise not go on to cause symptoms or death.” Overdiagnosis is not the same as misdiagnosis, which implies that the pathologist made a mistake looking at the specimen under a microscope. Overdiagnosis of cancer suggests that the cancer exists, but that it is clinically irrelevant – that left untreated, it would either regress spontaneously (we know this happens) or the patient would die of something else before the cancer caused symptoms or death. The authors describe how these overdiagnoses can harm patients and reduce quality of life. Such overdiagnoses lead to medically unnecessary procedures, such as radical surgery and treatments known to predispose to future cancers, such as chemotherapy and radiation, which can cause leukemia and other malignancies.
The authors of the study conclude, “Whereas early detection may well help some, it undoubtedly hurts others. In general, there is no right answer for the resulting trade-off—between the potential to avert a cancer death and the risk of overdiagnosis. Instead, the particular situation and personal choice have to be considered.”
But Doesn’t Mammography Save Lives?
Yes. It does. For every 2,000 women invited to screen for breast cancer over a period of 10 years, one death from breast cancer will be avoided (thank God!) but this life saved comes at a price. Ten healthy women – who didn’t need treatment because they would have never become symptomatic or died from their disease – will wind up diagnosed and treated for breast cancer unnecessarily.
Then why are doctors relentlessly pressuring women to get mammograms? Because early studies back in the 1980’s suggested that mammography reduced breast cancer mortality by up to 25%. More recently, the U. S. Preventative Services Task Force estimates that the benefit of mammography is about a 15% reduction in the risk of dying of breast cancer. But that assumes that every woman diagnosed with breast cancer would have died of it, and fortunately, treatments have improved so much that this is no longer true. Most women diagnosed with breast cancer based on screening mammography do not die from it.