Cancer treatment
Mammograms’ impact on breast-cancer deaths is small, study says
Carly Weeks
From Thursday's Globe and Mail
Published
Last updated
Routine mammograms have a relatively small impact on reducing the number of women who die from breast cancer, according to a study published Thursday in one of the world’s most respected medical journals.
The findings add more fire to the heated debate over the benefits of breast screening, one that continues to divide medical experts and confuse many female patients.
The study, conducted by researchers in Norway and published in the New England Journal of Medicine
“It’s just another proof that the mortality reduction is not as high as we expect it to be,” said Mette Kalager
Researchers used statistical and cancer data and records to look at four groups of women in Norway, aged 50 and 69, to get their results. One group of women participated in a universal breast-screening program that was rolled out in stages across the country from 1996 to 2005. Those women were compared with a similar group of women living in the same area 10 years earlier, before Norway adopted universal screening for breast cancer.
They also looked at a group of women who were aged 50 to 69 between 1996 and 2005 but who were living in an area that didn’t yet have the screening program up and running. Researchers compared that group to another group of women living in the area 10 years earlier.
After the results were tabulated, Dr. Kalager and her colleagues found that breast-cancer death rates declined by 18 per cent among the group who did not have access to a universal screening program, compared with the group from the previous decade.
The drop is attributed to improvements in treatment and care, as well as greater awareness of the disease.
When looking at the group who had participated in universal breast screening, researchers found their death rates declined by 28 per cent compared to the group from the previous decade. While it’s a major drop, it only represents an additional 10 percentage-point decline, or about one-third, when compared to women who had not been involved in a breast screening program.
“I think it’s very clear that the benefit that can be attributed to screening is very, very small,” said Cornelia Baines
But it’s even possible the 10-percentage-point mortality reduction is exaggerated, the study notes, because Norway has comprehensive breast-cancer management teams across the country and it’s impossible to tell whether the reduced death rate is due to screening programs or those improvements to treatment and care.
Anthony Miller
“I think we’re in an era where breast-cancer treatment has improved so much that it’s unlikely screening is going to make any major impact,” Dr. Miller said.
Yet, the idea that mammography is a crucial tool required to prevent breast-cancer deaths is ingrained in many parts of society.
Last year, the U.S. Preventive Services Task Force, an independent panel of experts, issued new guidelines stating that women in their 40s should no longer be recommended for routine breast screening, partly because of the risk of false positives. (False positives can lead to unnecessary additional tests and anxiety for patients.) But the guidelines were widely criticized by a variety of doctors, breast-cancer advocates and survivors of the disease.
In Canada, routine screening is recommended for women starting at age 50.
Jacques Lévesque, vice-president of the Canadian Association of Radiologists
The key to their success is how they are organized and ensuring that radiologists are well-trained, he said. “In my mind there is no doubt that screening is viable.”
But Dr. Baines, Dr. Miller and other experts question whether Canada places too much emphasis on mammograms. Dr. Miller said there needs to be a greater focus on other aspects of breast health, such as monitoring for changes and bringing concerns to doctors.
“I’d tell [women] that one of the most important things that they have to do is to be aware of their own breasts,” Dr. Miller said.