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New Canadian guidelines for breast screening

By: Sheryl Ubelacker

Posted: 11/22/2011 1:00 AM | Comments: 0 (including replies)

The Canadian Press archive New guidelines suggest most women age 50 to 69 can wait slightly longer between mammograms than previously recommended. (CP)

TORONTO -- Most women in their 40s should not have routine mammograms and those 50 to 69 can wait slightly longer between the tests than previously recommended, updated Canadian breast cancer screening guidelines advise.

And for the first time, the Canadian Task Force on Preventive Health Care that developed the guidelines says that women aged 70 to 74 should be getting mammograms on the same schedule as those 50 to 69.

The revamped guidelines, published Monday in the Canadian Medical Association Journal, apply to women with an average risk of developing the disease -- no previous breast cancer, no history of the disease in a first-degree relative like a mother or sister, no known BRCA genetic mutation and no previous exposure to radiation of the chest wall.

In its previous set of guidelines penned in 2001, the expert panel made no recommendations for average-risk women in their 40s as to whether they should have routine screening or not.

But the task force now advises against the practice for that age group, saying the potential harms from false positives and unnecessary subsequent cancer treatment outweigh the possible benefit -- a slight reduction in the number of deaths from the disease.

"Before there was no recommendation for or against, and clinical practice followed that lead," said task force chair Dr. Marcello Tonelli of the University of Alberta. "Most organized screening programs don't recruit women aged 40 to 49 years as a result.

"The biggest change of all is probably in the way in which we frame all of our recommendations, that breast cancer screening has risks and it has benefits, and how women weigh those up will influence their personal decision to be screened or not."

In the 2001 guidelines, women 50 to 69 with an average risk of breast cancer were advised to have mammography every two years. But the new guide extends that period, saying such tests can be done every two to three years.

The panel now suggests women age 70 to 74 should also have mammograms every two to three years.

"In routine practice, one of the challenges in producing guidance and then implementing it in real life is that patients don't turn up for screening or any other service on the anniversary of their last test," said Tonelli.

"So the intent here was to give a range so that someone who is appearing for screening at two years and a day is still falling within recommended practice (and) even after two years and six months," he said from Edmonton.

"We also wanted to signal that since the last set of guidelines were produced, there has been some evidence produced that longer screening intervals, like every three years, might be just as good as every year."

The new guidelines have grown out of an intensive review of international clinical trials, which looked at the risk of developing breast cancer in the various age groups and the potential harms inherent in the breast X-ray that can arise from misdiagnosis.

"Specifically, the harms could range from a woman being told she has an abnormality on a mammogram and being asked to repeat the mammogram, being asked to go for a biopsy of her breast, being asked to have part or all of her breast removed, and all the way up to surgery and radiation and chemotherapy.

"These are the spectrum of possible harms, so if you don't have breast cancer, but you have your breast removed and have surgery, I think we'd all agree that's a harm of screening."

The task force determined that screening 2,100 women every two to three years for about 11 years would prevent just one death from breast cancer. However, it also would result in 690 women having false-positives that would lead to unnecessary followup testing, including 75 women having unnecessary breast biopsies.

"For every woman that had cancer found with mammography, there are many more that have had a false positive result or a scare," Tonelli said.

-- The Canadian Press

Republished from the Winnipeg Free Press print edition November 22, 2011 A9

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