Women should be given the facts and left to decide whether to have mammograms, both critics and cancer support groups said in response to a controversial study that challenged the validity of the screening.
The study published last week by the New England Journal of Medicine concluded that “substantial overdiagnosis” affected more than one million women in the United States over a 30-year period from 1976 to 2008. It also estimated that one-third of women with breast cancer were needlessly treated – or received a false positive diagnosis – and that they would never have developed the deadly disease.
Dr. Jean Seely, head of imaging at the Women’s Breast Health Centre in Ottawa, is critical of the study, but said the main danger is the confusion that results from inconsistent findings when women are dealing with the choice to pursue screenings.
“The most important thing is for people to be properly informed,” Seely said. “Women should make the decision of what they want, knowing the facts.”
Health Canada says mammography is “the best tool available to screen for breast cancer in women,” and that it is used to find abnormal growths as well as to determine if women do not have breast cancer.
“My concern about these publications is it dissuades women from undergoing a test that is relatively harmless,” Seely said, adding that the majority of the false positives the study calculates would likely just mean a follow-up visit and less frequently results in an invasive procedure or biopsy.
“We just don’t know which ones are going to progress or not,” Seely said.
She also said Ontario has seen a 35 per cent decrease in mortality in cases of breast cancer in the last 20 years, which she connected to the initiation of massive population-based screening. And yet the U.S. study found that the use of mammograms resulted in only a slight decrease in the number of women with advanced cancer.
Willow Breast Cancer Support Canada provides emotional and practical support for people affected by breast cancer, as well as training to peer support groups across Canada. Local support groups in the Ottawa region include Breast Cancer Action Ottawa, a chat group for woman at-risk for hereditary breast or ovarian cancer and a support group in Kanata.
Jeff Beach, Willow’s executive director, said its approach to requests for information is to provide support specific to each woman on a case-by-case basis. He said that the study’s findings won’t change how they provide that support.
“I think what the study is showing is that there are certain types of breast cancer that are not necessarily aggressive in nature,” Beach said, “but they may be treated because they were picked up in a mammogram and otherwise wouldn’t even be noticed.”
Beach said the study is just another thing for women to consider.
“I wouldn’t say it’s problematic,” Beach said. “Our role is to educate and empower people to help them make the best decisions for the best possible health outcomes.”
The research on mammography has been in disagreement before – this is one of the latest in a string of studies related to the subject that range from their usefulness to the age when women should begin thinking about mammograms.
This morning, Dr. Marla Shapiro (a breast cancer survivor and medical correspondent for Canada AM) pointed to two recent studies that contradict the current study’s findings on mammograms. The first was a U.K. panel that indicated screenings resulted in overdiagnosis, but that they also have reduced breast cancer deaths.
The second was a U.S. study that investigated the impacts of less stringent guidelines on screenings. The study found that the “new recommendations may lead to missed cancers and a decline in screening.”
In September, Robin Bell, a medical epidemiologist and associate professor at Monash University in Australia, published findings that also indicated unnecessary over-diagnosis from mammography, going further to suggest that decreases in mortality rates were due to better cancer treatment rather than early detection.
It isn’t clear from the studies how to determine whether a diagnosis is a false positive.
“The issue of over-diagnosis is not one we can totally blow over. I’m not minimizing it,” Seely said, noting if they could determine which cancers would progress “we would be ahead of the game, but I think to throw the baby out with the bathwater would be a big mistake.”