Missing key research, Canada’s mammography guidelines were built on flawed research, new study finds

Many women in Canada have had their breast cancer screening policy based on flawed research by someone who was disqualified from conducting the research, according to researchers who have studied the data.

Researchers studied data for a group of women aged 40 to 69 who were initially screened between 1979 and 1985 by the Canadian Cancer Society, according to The Guardian. They found that women who received abnormal mammograms later on were 41 percent more likely to die of breast cancer than women who didn’t receive any abnormal mammograms. This led officials to set up a mammography policy in Canada: Everyone over 40 received screening mammograms every two years, and anyone who didn’t go to a regular doctor for more than two years, or skipped their regular screening regularly, would get letters in the mail notifying them that they were not getting a mammogram. These women were told they were exempt if they were told by their doctor that they were likely to die of something else first.

This made sense to many physicians and women who had originally opted for the annual screening. But the researchers found that the outcomes didn’t match up with what the study had actually found.

“The study cohort was made up of women who had been treated for breast cancer for an average of 21 years; study authors wanted to see if the in-depth treatment history of their cancer might actually influence subsequent death rates,” the study reads.

However, when data from several studies from other groups were pulled from and compared to those from the Canadian Cancer Society study, results “all showed one thing: that there was no difference in death rates between those women who received routine screening mammograms and those who did not,” the study reads. The researchers behind the study also found that among these women who did die, death rates were 42 percent higher for those who opted for regular mammograms.

“Given the overlap of in-depth histories with treatment histories and because the differences in the gender and age distributions of postscreening death rates remained in our research, it is hard to see how routine mammography screening could possibly have prevented cancer death among this group of patients,” the study reads.

Olivia Cochrane, a senior researcher at the Population Health Research Institute of Ottawa, who co-authored the report, told The Guardian that they had found “likely evidence of bias” in the research that produced the mammography guidelines for Canadian women in 1979.

“This research provides the first evidence that the early detection and elimination of breast cancer by routine screening is fundamentally ineffective and undermines the conclusions of the national guidelines,” she told The Guardian.

Read the full story at The Guardian.


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