There has been a great deal of confusion over the past several years about how much benefit most women can expect from the annual mammogram. Cancer organizations have argued over the best age for healthy women to start undergoing this screening procedure. Recently, there has also been a recognition that some women who go in for a mammogram will get a false positive result that may involve invasive follow-up, even though they do not actually have breast cancer.
A special communication published in JAMA Internal Medicine finally offers some figures on how common such false alarms seem to be. It also gives an estimate of the number of women who need to get a screening so that one woman will be able to avoid death from breast cancer. You might be surprised to learn that if 1,000 50-year-old women are screened every year for 10 years, between 3 and 0.3 of them will have a life-threatening breast cancer found and successfully treated.
On the other hand, among these same 1,000 hypothetical middle-aged women, between 3 and 14 will be overdiagnosed with breast cancer and treated unnecessarily. Around half of these women (490 to 670) will have at least one false alarm during the decade, an event that causes anxiety at the very least, and often leads to further testing with potential complications. The authors hope that having these statistics will help women decide whether they want to undergo screening mammography or to discuss the pros and cons of breast cancer screening with their physicians if they are unsure.
[JAMA Internal Medicine, online Dec. 30, 2013]
As always, the definition of screening means that the women getting mammograms have no symptoms. No one doubts the value of mammography for investigating a new breast lump or other symptom.
You can read more about our take on mammography here.
If you would like to hear on of the authors of this special communication discuss overdiagnosis, you can listen to our hour-long interview for the radio.
