A recently published article about screening mammography for breast cancer is attracting considerable media attention and, once again, is confusing women about the importance of screening. The controversy should not be allowed to obscure a basic fact: Annual mammograms save lives.
The article by Dr. Anthony Miller and others, published in the British Medical Journal, reports long-term findings of the Canadian National Breast Screening Study (CNBSS). Leading researchers have widely discredited that study, citing its flawed design and poor techniques.
The scientific community excluded the Canadian trial data from a World Health Organization analysis of screening mammography back in 2002 — and Dr. Miller headed the panel that made that decision. We can only wonder why he would come to a different and completely unsupportable conclusion in 2014, threatening the lives of women around the world.
Here are just some of the profound limitations of the Canadian study:
● The equipment used in the study was out of date. The mammography technologists had no training in proper positioning and technique. The study did not use standard components of a correctly done mammogram, which lower radiation doses and markedly improve image quality
The supervising physicist for the study has stated: “I identified many concerns regarding the quality of the mammography carried out in the CNBSS screening centers. That quality was far below the state of the art, even for the early 1980s.”
● The radiologists who read the exams had no specific training in interpreting mammography. Their performance wasn’t close to what experienced — and in many cases expert — breast-imaging radiologists offer.
● Fewer than one-third of the cancers that developed among patients in the study were detected by mammography alone. That number should have been about 70 percent. A failure to find half the cancers that should have been detected is bad mammography.
● The division of patients in the study between those who got mammograms and those who did not was not truly random. Before they were enrolled in the study, all patients got breast exams by trained nurses. Those with lumps in their breast or armpits were placed in the screening group and got mammograms.
This placement of many patients with cancers — often advanced — into the screening group skewed the numbers of cancer cases and deaths in that group, and away from the control group. In the 1980s, the overall five-year rate of surviving breast cancer among Canadian women in their 40s was 75 percent. For patients in the study’s control group, the survival rate was 90 percent.
These flaws in the CNBSS have been known for years. Yet incorrect and dangerous conclusions drawn from its flawed data continue to be advanced. We are left to conclude that those who make these assertions seek to limit screening as a cost-saving measure. Those who are dedicated to the health of their patients know better, and do better.
We join the American Cancer Society, the Society of Breast Imaging, the American College of Obstetricians and Gynecologists, and dozens of other scientific and public-interest groups in telling our friends, loved ones, and patients to get annual mammograms starting at age 40. They have been proved to save lives. Don’t let anyone tell you otherwise.
Daniel A. Dessner, M.D., is president of Toledo Radiological Associates. Robin B. Shermis, M.D., is director of ProMedica’s Breast Care Center.