New report on contentious breast cancer screening study divides researchers

A new paper calls into question the scientific process behind the Canadian National Breast Cancer Screening Study from the 1980s, a contentious subject that has divided researchers for years.

Researchers from Toronto's Sunnybrook Research Institute, the Ottawa Hospital, the University of British Columbia, the University of Alberta and Harvard Medical School published their examination of the CNBSS in the Journal of Medical Screening this week, alleging that the original study had significant flaws, particularly in the randomization aspect of the research.

The CNBSS was a series of trials done in the 1980s at 15 screening centres in six provinces: Nova Scotia, Quebec, Ontario, Manitoba, Alberta and British Columbia. Close to 90,000 women aged 40 to 59 participated in the study.

Its purpose was to determine whether cancer screening programs helped saved women’s lives, and assigned the participants into two groups – one with women aged 40 to 49 and 50 to 59 that received mammograms and another control group where both age sets had a single physical exam.

All participants were followed by the study for several years.