The scientific panel tasked with sorting out the conflicting signals on breast-cancer screening has only inflamed the debate and left women – and their doctors – even more confused.
New guidelines, written by the Canadian Task Force on Preventive Health Care, are designed to clarify best practices for screening at a time when many experts and advocacy groups remain sharply divided, particularly about the benefits of routine mammograms for women in their 40s.
The long-time approach to screen early and often has now met a new wave of research and recommendations that concludes that routine mammograms for women in their 40s are of negligible benefit and can lead to needless procedures.
The controversy – playing out against the backdrop of a strapped health-care system that has to make hard decisions about resources and costs – has been stirred by the new national screening recommendations, which say Canadian women under age 50 who are at an average risk of developing breast cancer should not have routine mammograms, and that also advises against self-exams at any age.
In addition to limiting mammograms to women age 50 to 74, the guidelines also say clinical breast exams and self-exams have no benefit and shouldn't be used; that women aged 50 to 69 should have mammograms every two to three years, instead of every year or two; that women aged 70 to 74 should have mammograms every two to three years – previous guidelines didn't recommend screening for that age group.
The recommendations don't apply to women with an elevated risk of breast cancer, such as those with a history of the disease in a first-degree relative or those with mutations in the BRCA1 and BRCA2 genes.
But instead of quelling debate, the recommendations are opening a new chapter in the simmering battle.
While many oncologists and groups such as the Canadian Cancer Society say the new recommendations, published Monday in the Canadian Medical Association Journal, are a balanced approach that will focus breast cancer screening programs on women who can benefit most, others believe the move to limit mammograms to those age 50 and over will put lives in danger.
"We're really disappointed to see these recommendations," said Sandra Palmaro, CEO of the Canadian Breast Cancer Foundation, Ontario region. "They're ultimately going to result in more women dying from breast cancer that don't need to be dying from breast cancer, there's no question."
Provinces are responsible for breast cancer screening programs. Many, such as British Columbia, Alberta and Nova Scotia, regularly give mammograms to women aged 40 to 49, while some others, including Ontario and Newfoundland and Labrador, do not. It remains to be seen whether provinces choose to adopt the new guidelines.
At the heart of the debate is an argument about the merits of cancer screening programs. Proponents of mammograms for women in their 40s say they can save lives by detecting cancer early.
But more recently, the tide has been shifting away from the notion that more screening is better. For instance, a U.S. panel ruled in 2009 that women in their 40s should not be screened for breast cancer. The backlash from advocacy groups and experts was so fierce that the rules haven't been adopted.
Last weekend, the screening controversy showed up in the medical journal The Lancet, which published a letter signed by more than 40 physicians and radiologists, including three Canadians, who detect an "active anti-cancer screening campaign" among a particular group of scientists. The campaign, they say, is marked by "erroneous interpretation of data from cancer registries and peer-reviewed articles."
Still, more experts in Canada have begun questioning whether support for screening programs has been too zealous, responding to growing scientific evidence suggesting that mammograms for women aged 40 to 49 may not save many lives, but can lead countless women to have unnecessary follow-up treatments and biopsies.
"I think we're in a situation where there's been question marks about screening mammography," said Eitan Amir, medical oncologist at Princess Margaret and Mount Sinai hospitals in Toronto.
A Danish study published in the British Medical Journal last year, for instance, found little difference in breast cancer mortality rates among women who had routine mammograms and those who did not.
Using evidence from previously conducted studies, the Canadian Task Force on Preventive Health Care found that more than 2,100 women aged 40 to 49 would need to be screened regularly for an 11-year period to prevent one breast cancer death. At the same time, it would cause nearly 700 women to have a false-positive mammogram result and needless follow-up, with 75 of those women having an unnecessary biopsy. For women aged 50 to 69, the number needed to be screened to prevent one breast cancer death is 721.
Despite shifting evidence, it will be difficult to change the dialogue because the perceived benefits of mammography have become ingrained, experts say. Compounding the problem is the fact that some advocacy groups and medical experts continue to publicly champion the notion of more screening at earlier ages, which may confuse women.
"Certainly there's always going to be groups that try to sensationalize this stuff," said Gillian Bromfield, director of cancer control policy at the Canadian Cancer Society. "I think it is concerning when we scare women into screening, no matter what their age."