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.
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 inthe Journal of Medical Screening this week.
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 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.
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.
As 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.
The study has gone on to inform guidelines both here and around the world. 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.
Experts have warned any kind of breast cancer treatment — whether it be radiation, chemotherapy or surgery — may carry harm.
New evidence
But the CNBSS had several problems, according to Dr. 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.
She and her co-authors are calling for mammograms for women aged 40 or older, should they want them.
Seely said there is now “conclusive confirmation” the CNBSS was conducted — particularly in some trial locations — with women who weren’t randomly assigned.
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.
“I was astonished. I did not expect to find such clear, clear evidence of what was going on,” Seely said. “Then I think my next reaction was anger. How could this have been allowed?”
Dr. Jean Seely is a professor of radiology at the University of Ottawa and head of breast imaging at The Ottawa Hospital. She is also the author of the paper recently published in the Journal of Breast Imaging. (Michel Aspirot/CBC)
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.
Experts have mostly suspected issues with the randomization, which they say would’ve skewed the findings.
The resulting paper said it “failed to uncover credible evidence” that the randomization was subverted in any way. 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
Still, some experts aren’t convinced; the new paper concludes that results of the trial would have changed with the seven instances of women with lumps from the mammography group sent to the usual care group.
Seely said she’s hopeful this new evidence will lead to change
“I think probably the most personal challenging moments that I have in my practice are when I see a woman in her 40s who presents with an advanced breast cancer,” she said.
More often than not, Seely said, those women were told by their family doctors they shouldn’t be screened because of their age. “On a personal level, as a professional, I find this very, very difficult,” she said.
According to the Canadian Cancer Society, while women aged 50 and older have higher rates of breast cancer diagnosis, there’s a higher rate of mortality for women between 30 and 49.
Women in that age range consist of 17 per cent of all cancer deaths in Canada. That’s compared to women aged 50-69, who represent just eight per cent of cancer deaths.
Lead investigator defends study
Many other experts, including the principle investigators of the CNBSS, continue to defend the study.
“We had a great deal of understanding of what could go wrong with randomization and we took a great deal of care to ensure it didn’t apply in the National Breast Screening Study,” said Dr. Anthony Miller, a professor emeritus at the Dalla Lana School of Public Health at the University of Toronto, who led the study.
Miller, who has seen a copy of the new paper, denies the possibility that any women were not placed randomly within the trials. There were extensive quality-control measures in place to maintain the integrity of the study, he said.
One of the primary reasons it is not recommended women that in their 40s undergo regular mammograms is the risk of over-diagnosis. (CBC)
Nurses were only in place to inform participants about the study and get their consent, he said, and any examinations happened after a woman had been randomized.
At that point, Miller said, excluding women who may have had palpable lumps “would indeed falsify the results of the study.”
CNBSS considered gold standard
Miller is not alone in his defence of the CBNSS. While its authors say their work has been under attack for decades, the CBNSS has withstood years of skepticism and challenges.
Compared to a number of other breast cancer screening trials, it would be difficult to find one as well documented and well run as the CNBSS, according to Dr. Karsten Jørgensen, acting director of the Nordic Cochrane Centre, which reviews medical trials, including those on breast cancer screening.
Canada’s trial results also align with other reputable studies around the world, which show no benefit to early screening, Jørgensen said.
“There’s always room for interpretation. There’s also always pitfalls. There’s always limitations with the trials — but that’s why we do systematic reviews and these types of meta-analysis,” said Jørgensen.
“Much of this is down to interpretation and which results should you trust.”
New findings being considered
Seely and her fellow researchers have raised their concerns about the CNBSS to the University of Toronto and the Canadian Medical Association Journal, both of which were involved in the original study.
In a statement, the university’s office in charge of research, oversight and compliance said it “places a high value on research integrity” and is “reviewing the concerns raised by a group of individuals and has been in touch with them.”
The university did not specify the scope or timeline of its review, only that it will “get back to them with our next steps.”
“CMAJ will co-operate with the university office’s process fully and will await the office’s report on the outcome of the review before deciding if any further action is needed,” Dr. Kirsten Patrick, interim editor-in-chief of the journal, wrote in her own statement.
She did not provide any further comment.
Unlikely guidelines will change
The Canadian Task Force on Preventive Health Care says it is unlikely it will consider changing the country’s current guidelines on breast cancer screening to include women in their 40s.
In a written response to CBC, the task force defended its guidelines, saying it “conducts rigorous, detailed evidence reviews” when formulating them.
“Our guidelines, including those on breast cancer screening, have been recognized as the best in the world,” said Dr. Brenda Wilson, co-chair of the task force.
Wilson wrote “the best available evidence” is used to inform the guidelines. When there are changes to that evidence, she said the task force “updates a full review of the body of evidence, including any new evidence.”
The task force doesn’t comment on individual studies or opinion pieces without doing that review, she said.
HALIFAX – The Nova Scotia government says it could be months before it reveals how many people are on the wait-list for a family doctor.
The head of the province’s health authority told reporters Wednesday that the government won’t release updated data until the 160,000 people who were on the wait-list in June are contacted to verify whether they still need primary care.
Karen Oldfield said Nova Scotia Health is working on validating the primary care wait-list data before posting new numbers, and that work may take a matter of months. The most recent public wait-list figures are from June 1, when 160,234 people, or about 16 per cent of the population, were on it.
“It’s going to take time to make 160,000 calls,” Oldfield said. “We are not talking weeks, we are talking months.”
The interim CEO and president of Nova Scotia Health said people on the list are being asked where they live, whether they still need a family doctor, and to give an update on their health.
A spokesperson with the province’s Health Department says the government and its health authority are “working hard” to turn the wait-list registry into a useful tool, adding that the data will be shared once it is validated.
Nova Scotia’s NDP are calling on Premier Tim Houston to immediately release statistics on how many people are looking for a family doctor. On Tuesday, the NDP introduced a bill that would require the health minister to make the number public every month.
“It is unacceptable for the list to be more than three months out of date,” NDP Leader Claudia Chender said Tuesday.
Chender said releasing this data regularly is vital so Nova Scotians can track the government’s progress on its main 2021 campaign promise: fixing health care.
The number of people in need of a family doctor has more than doubled between the 2021 summer election campaign and June 2024. Since September 2021 about 300 doctors have been added to the provincial health system, the Health Department said.
“We’ll know if Tim Houston is keeping his 2021 election promise to fix health care when Nova Scotians are attached to primary care,” Chender said.
This report by The Canadian Press was first published Sept. 11, 2024.
ST. JOHN’S, N.L. – Newfoundland and Labrador‘s chief medical officer is monitoring the rise of whooping cough infections across the province as cases of the highly contagious disease continue to grow across Canada.
Dr. Janice Fitzgerald says that so far this year, the province has recorded 230 confirmed cases of the vaccine-preventable respiratory tract infection, also known as pertussis.
Late last month, Quebec reported more than 11,000 cases during the same time period, while Ontario counted 470 cases, well above the five-year average of 98. In Quebec, the majority of patients are between the ages of 10 and 14.
Meanwhile, New Brunswick has declared a whooping cough outbreak across the province. A total of 141 cases were reported by last month, exceeding the five-year average of 34.
The disease can lead to severe complications among vulnerable populations including infants, who are at the highest risk of suffering from complications like pneumonia and seizures. Symptoms may start with a runny nose, mild fever and cough, then progress to severe coughing accompanied by a distinctive “whooping” sound during inhalation.
“The public, especially pregnant people and those in close contact with infants, are encouraged to be aware of symptoms related to pertussis and to ensure vaccinations are up to date,” Newfoundland and Labrador’s Health Department said in a statement.
Whooping cough can be treated with antibiotics, but vaccination is the most effective way to control the spread of the disease. As a result, the province has expanded immunization efforts this school year. While booster doses are already offered in Grade 9, the vaccine is now being offered to Grade 8 students as well.
Public health officials say whooping cough is a cyclical disease that increases every two to five or six years.
Meanwhile, New Brunswick’s acting chief medical officer of health expects the current case count to get worse before tapering off.
A rise in whooping cough cases has also been reported in the United States and elsewhere. The Pan American Health Organization issued an alert in July encouraging countries to ramp up their surveillance and vaccination coverage.
This report by The Canadian Press was first published Sept. 10, 2024.
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