Last week, the Canadian Task Force on Preventive Health Care released the new screening guidelines for women with an average risk of developing breast cancer. The guidelines recommend that women under 50 do not have screening mammograms. Click here to read our coverage of the guidelines.
Here, scientist Martin Yaffee comments on why he rejects most of the new breast-cancer screening guidelines. Click here to read Dr. Cornelia Baines's comments on why she supports them.
When I began my work as a breast cancer researcher in 1978, my goal was to improve mammography to save women’s lives. I helped develop digital mammography and tested it in a clinical trial with 50,000 women in the U.S. and Canada. In 2005 in The New England Journal of Medicine, we reported that for women under 50 and, especially for those with dense breasts, digital was significantly more accurate than film in finding breast cancer. Our current goal is to develop a better way than mammography to detect breast cancer. There are some promising ideas but we’re not there yet. Until that happens mammography is the best proven tool for saving lives. I have been carefully reading the science related to breast cancer detection for over 30 years and based on the evidence I must reject most of the Task Force recommendations on breast cancer screening.
One sixth of breast cancer deaths and 40 per cent of years of life lost come from cancer that arises from women in their 40s. All the fuss that’s been in the news is not because earlier detection of breast cancer with screening doesn’t save lives. It does. Even the Task Force, despite not recommending screening for women in their 40s, agrees it reduces deaths by 15 per cent. And that’s with antiquated 1980s mammography; with modern technology it’s more like 24 per cent. By the way, that study was from before digital mammography was introduced – we should be able to do better for women under 50 now. Most oncologists agree that this benefit comes from being able to use improved therapies on less advanced cancers found through screening. It’s the combination of these two factors that provides the benefit.
There are additional benefits to earlier detection. When cancers are less advanced, chemotherapy may not be necessary – reducing harm to the patient and costs for the health care system. The female doctors I work with know this and many of them (women at average risk for breast cancer), some who are leading breast oncologists who treat women with breast cancer every day, have gone for screening since they were in their 40s. But currently, some provinces like Ontario where we live, won’t allow women in that age group into their screening program. And if they heed the Task Force, they never will.
We all agree that mammography isn’t perfect – it misses some cancers, finds some that aren’t potential killers and finds others too late. At a given time, most women don’t have breast cancer. We have to screen a lot of women to find the few who do and potentially save their lives. These are shortcomings of screening, not harms. The Task Force has used language that distorts the facts. An example is “false positives”, which they identify as a major harm. Consider this: for 93 per cent of women screened, a single 4-image mammography exam allows the doctor to determine that she doesn’t have breast cancer. For the other 7 per cent, some additional non-invasive imaging views are required. Is that an unacceptable harm? But that 7 per cent is what the Task Force calls “false positives” and considers to be harmful enough to outbalance the potential to save lives.
