Women in their 40s could benefit from annual breast screenings, say U.S. radiologists in a finding that adds to the confusion on the best use of mammography.

The research was presented at the Radiological Society of North America's annual meeting in Chicago on Tuesday. 

"We believe this study demonstrates the importance of mammography screening for women in this age group, which is in opposition to the recommendations issued by the task force," Dr. Stamatia Destounis, a radiologist and managing partner of Elizabeth Wende Breast Care in Rochester, N.Y., said in a release, referring to task force guidelines in the United States.

Last week's guidelines in Canada also advise against routine mammography for women of average risk of breast cancer who are in their 40s.

"It's difficult to draw conclusions from this one study," CBC's medical specialist Dr. Karl Kabasele said of the radiologists' findings. 

"Whereas when you look at the new Canadian guidelines, they're actually based on a review of a wide range of research, and that’s where the idea that women between the ages of 40 and 49 may have more harms associated with regular mammograms than benefits." 

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The radiology study looked at the number and type of cancers diagnosed among women between the ages of 40 and 49, with and without a family history of breast cancer. (Rich Pedroncelli/Associated Press)

The study was not peer-reviewed, meaning no researchers independently critiqued the methodology — a system of checks and balances that is often in place before a study is published in a medical journal rather than presented at a conference.

Last week's guidelines from the Canadian Task Force on Preventive Health Care suggested routine mammograms for women in their 40s offered the potential for harm from over-diagnosis and unnecessary biopsy and even unnecessary mastectomies, radiation and chemotherapy, with no significant benefit.

Previously, some Canadian provinces already routinely screened women in their 40s. British Columbia announced it would continue to do regardless of the new national guidelines.

A woman in her 40s at average risk of developing breast cancer may still get the screening if she wants one, noted Dr. Ruth Wilson, a family physician in Kingston, Ont. Wilson is also associate director of health policy for the College of Family Physicians of Canada, which endorsed the Canadian task force's recommendations.

When the U.S. Preventive Services Task Force released similar breast cancer screening guidelines in November 2009, it sparked a controversy among physicians, patient advocacy groups and the media. Much of that debate centered on the recommendation against routine annual mammography screening for women in their 40s.

The radiology study presented Tuesday looked at the number and type of cancers diagnosed among women between the ages of 40 and 49, with and without a family history of breast cancer, between 2000 and 2010. Some of the women, 373, had screening.

Invasive cancer was diagnosed in 64 per cent of cases presenting without family history and 63 per cent with family history, the researchers said.

Some of the study's authors said they had ties to companies that supply screening equipment.

With files from The Canadian Press