Still, some experts aren't convinced the new paper concludes that results of the trial would have changed with just seven instances of women with lumps from the mammography group sent to the usual care group. Its authors further said that even if there had been acts of subversion, they would have been "few in number" and "alterations could have had only a trivial effect on the study findings." Results would be different, experts argue The resulting paper said it "failed to uncover credible evidence" that the randomization was subverted in any way.
Since the '90s, radiologists and researchers have raised concerns about the inclusion of women with advanced cancers in the study, the quality of the screening and the factors used to determine if mammographies were beneficial for that age group.Įxperts have mostly suspected issues with the randomization, which they say would've skewed the findings.Īn investigation into these suspicions was done by external experts in the 1990s after the first results of the CNBSS were published. The paper adds to the long-standing debate over the quality of the studies since they were first published and whether women in their 40s should be regularly screened. She is also the author of the paper recently published in the Journal of Breast Imaging. Jean Seely is a professor of radiology at the University of Ottawa and head of breast imaging at The Ottawa Hospital. "Then I think my next reaction was anger. I did not expect to find such clear, clear evidence of what was going on," Seely said. When interviewing 28 staff members who worked on the original study, some confirmed there were multiple instances in which women with detectable lumps, who were pre-screened by a nurse, were in fact purposefully placed in the mammography group, she said. Seely said there is now "conclusive confirmation" the CNBSS was conducted - particularly in some trial locations - with women who weren't randomly assigned.
She and her co-authors are calling for mammograms for women aged 40 or older, should they want them. Jean Seely, co-author of the new paper and a professor of radiology at the University of Ottawa and head of breast imaging at The Ottawa Hospital. New evidenceīut the CNBSS had several problems, according to Dr. There are lumps that aren't cancerous or harmful to women, but if discovered, would require a biopsy.Įxperts have warned any kind of breast cancer treatment - whether it be radiation, chemotherapy or surgery - may carry harm. Breast cancer death rates in Canada didn't improve with mammogramsĪ key issue of earlier screening is the risk of false positives and over-diagnosis.Something may be missing in the new breast cancer screening guideline.The most recent guidelines issued by the Canadian Task Force on Preventive Health Care still do not recommend screenings for women in that age group. The study has gone on to inform guidelines both here and around the world. Over the course of the study, there were 38 deaths from breast cancer in the mammography group and 28 among those who didn't receive mammogram screenings.Īs a result, Canadian researchers concluded that annual screening in women aged 40 to 49 at average risk does not reduce breast cancer mortality any more than a physical exam.Ģ:06 A new paper is questioning a decades-old Canadian breast cancer screening study and calls for changes to Canada's guidelines, allowing more women in their 40s to be routinely screened. The randomized trials set out to determine whether or not screening helped save women's lives. In the first study, women aged 40 to 49 were randomly assigned to receive mammograms or placed in a control group where they had a single physical exam, with all participants followed up with for several years. It specifically points to randomization issues with the Canadian National Breast Screening Study (CNBSS), originally conducted in the 1980s, which involved tens of thousands of women and eventually took place in 15 different urban centres across the country. The commentary - co-written by researchers at The Ottawa Hospital, Sunnybrook Research Institute in Toronto, the University of British Columbia, the University of Alberta and Harvard Medical School - will be published in the Journal of Medical Screening this week. A new paper calls into question a decades-old Canadian study that has informed breast cancer screening guidelines for women in their 40s around the world, which generally do not recommend a yearly mammogram.