Are too many women getting mammograms unnecessarily?
This question has been increasingly raised as concerns over the effectiveness of mammography to prevent breast cancer deaths have been debated. The latest iteration came in February when the 25-year update to the Canadian National Breast Screening Study was published in the British Medical Journal. The study concluded that annual mammography in women aged 40 to 59 years did not reduce breast cancer deaths beyond that of physical examination.
Still, among leading American policy and women’s health organizations, the answer to whether mammograms are being overused is a resounding “NO!”
Instead, experts lament stagnate screening rates and fear that the message of mammography’s benefit is being lost in the conversation, with physicians steering clear of what has become a somewhat contentious debate.
The American College of Obstetricians and Gynecologists (ACOG), the American Cancer Society, and the American College of Radiology all criticized the results of the Canadian study. They pointed to flaws in the screening technology employed, trial design, misleading analysis, incomplete reporting in the general media, and a failure by those embracing the study to remember other major mammography trials that have pointed to a vastly different conclusion.
“I think because screening trials and data are complex that to truly glean meaning from them you have to dig down into the details,” said Richard Wender, MD, chief cancer control officer, American Cancer Society. “The way the media has portrayed the results is to say the study defines the science rather than letting the science dictate how women should respond and behave.”
One particular point of contention with the Canadian study is that the quality of the mammography machines used in the study are outdated and poor, explained Carol Lee, MD, chair of the American College of Radiology Breast Imaging Communications Committee. The images produced by the older technology were cloudy and made it more likely for cancers to be missed by radiologists, she said.
“Paying a lot of attention to the Canadian study is, to me, analogous to relying on a weather report from last week to tell us if it is raining outside today,” Lee continued.
For example, the study results indicated that 66% of the women had more advanced tumors that were big enough to be felt on physical exam at the time of mammography screening. “With modern mammography screening today, only 15% of breast cancer tumors can be felt; this means that more early-stage tumors that are missed by clinical breast exams are caught by mammograms when they are very small and more easily treated,” ACOG pointed out in a statement issued after the Canadian study was published in BMJ.
In addition, the Canadian study results were already an outlier when first reported, Wender said.
“Frankly, it didn’t provide any new information that wasn’t already known,” he said. “When we’ve had a study that has already shown no benefit, the likelihood that a benefit would emerge on follow-up analysis is just about zero.”
Furthermore, despite being an outlier, Wender pointed out that the study was considered and included in meta-analysis used by the American Cancer Society and the U.S. Preventive Services Task Force in providing guidelines for mammography. ACOG also included the study in forming its recommendation for annual mammography to commence at 40 years of age in women at average risk for breast cancer. ACOG reiterated its stance in its statement.continued