Study Unveils Mammography Doubts


Breast cancer is the second leading cause of death among women in North America. Approximately one in 30 women die of breast cancer.

While the benefits of mammography for postmenopausal women are clear, it is less defined for women in their 40s. To add to the confusion, the Canadian National Breast Screening Study (CNBS) of 50,000 women over 40, recently released its findings on mammography in the Annals of Internal Medicine. The study shows that the mammogram doesn’t lower the death rate for breast cancer in women over 40.

The findings of this study are very troubling to patients and physicians alike – as to whether the disease was detected by mammogram or breast exam, the resulting breast cancer deaths are still identical. In an age of early detection, new digital technologies, and accredited radiologists, how are these findings still possible?

“This study (CNBS) is one part of the consideration,” said Mr. Norman LaBerge, CEO, of The Canadian Association of Radiologists. “The patient and the doctor need to follow up on all the information received, as to whether it is positive or negative. It should be the patient’s choice for a mammogram between 40-49 that is in that category, based on all considerations, risk factors and benefits.”

“It is the overall results, across all of these studies that are beneficial (CNBS study is in its third time publication),” noted Dr. Mai, Director Screening Program at Cancer Care Ontario. Dr. Mai thinks the best approach is to review them altogether as a summary.

The study’s results have led Dr. Mai to create a summary of the recommendations from the reviews of the Canadian and the US Task Forces, and the International Association Research for Cancer. “These are three credible bodies with each of their recommendations. There aren’t major differences. There is reasonable agreement that there is more benefit than harm from screening. Mortality is reduced,” said Dr. Mai. “The underlying question is do women in their 40s really experience a lower death rate?”

“The study is not current, and it suggests mammograms do not reduce breast cancer deaths,” said Dr. Martin Yaffe, Senior Research Scientist and Specialist in Breast Imaging Systems, Sunnybrook and Women’s College Health Sciences Centre. Dr. Yaffe says the Study is described as a recent study that actually began in 1980. “The technology that was available at the time this study began is not comparable to what is used today. Every (mammography) aspect has improved, including knowledge and interpretation, and radiologists’ training programs that didn’t exist at that time. It is dangerous to compare and draw conclusions based on mammography done at that time to what we do at present.”

“This (study) tracks 13 years of new findings on old data,” continued Mr. LaBerge. ” It was just six years ago that The Canadian Association of Radiologists was saying screening wasn’t appropriate unless there were risk factors. That decision changed three years ago.” The association now says mammograms should be conducted on women 40 -49.

” Mammograms in the 80s were totally different than today. In the 80s the test wasn’t efficient, unless quality was a major component. Accreditation for radiologists was decided in 1992…. The major difference is quality control.”

Dr Andrea Miller, a radiologist at St. Joseph Health Centre in Toronto, has another suggestion. It’s media attention. There’s too much of it and it causes confusion for patients and physicians. When patients ask her about the study’s results, she says the Canadian study is different from the US Task Force findings, and even those in Europe. “I’m approaching 40,” said Dr. Miller. ” When my friends ask if I’m going to, I say get a mammogram after 40.”

Are mammograms effective?Although the controversy for mammograms is greatest in women 40-49, the answer is still yes, they are necessary. Mammograms can identify cancers before lumps on the breast are felt. The goal of screening mammograms is to identify breast cancers before they spread.

Dr. Yaffe strongly believes women should continue to have routine mammograms in their 40s, and it should be part of an organized program, such as the Ontario Breast Screening Program, at a facility which is accredited by the Canadian Association of Radiologists. LaBerge has his own theory. In Canada, accreditation wasn’t well structured in the 80s, and in the 90s more than half of the centres had failed testing. Any mammogram collected at that time would be hard to study – add to this the introduction of digital mammography. “Follow the study as to when they introduced the screening program, and you can actually see the drop in death rates and aggressive drops in breast cancers.” LaBerge concludes, “These key elements can’t be considered in a scientific study because of the controlled environment cutting into other factors.”

The full report is titled “The Canadian National Breast Screening Study-1: Breast Cancer Mortality after 11 to 16 Years of Follow-up. A Randomized Screening Trial of Mammography in Women Age 40 to 49 Years.” It is in the 3 September 2002 issue of Annals of Internal Medicine (volume 137, pages 305-312). The authors are AB Miller, T To, CJ Baines, and C Wall.