Mammograms for women in their 40s could help some at high risk of breast cancer, a new analysis suggests.

In Monday's online issue of the Annals of Internal Medicine, U.S. researchers looked at the benefits of screening in terms of breast cancer deaths averted. They also weighed the harms from false-positive mammography exams that sometimes lead to extra procedures, pain and anxiety.

"Our research suggests the benefit-harm balance is tipped in favor of every-other-year screening for women in their 40s who are at about twice the average risk of developing breast cancer," the study's senior author, Dr. Jeanne Mandelblatt of Georgetown Lombardi Comprehensive Cancer Center in Washington, said in a release.

Whether the benefits of mammography outweigh the potential harms has been called into question this year, particularly for women aged 40 to 49.

Mammography aims to detect breast cancer when it is localized and curable to prevent advanced disease and breast cancer deaths.

Conditions the U.S. researchers said double the risk of breast cancer include:

• Having extremely dense breasts (13 per cent of the population aged 40 to 49).
• Having a parent, sibling or child with breast cancer (9 per cent of the population aged 40 to 49).

In comparison, factors such as current use of oral contraceptives, never giving birth to a child, or giving birth to a first child after age 30 increased a woman's risk of breast cancer by 1.0- to 1.5-fold.

Individual guidelines

The researchers said they hope the results will guide the development of individualized, risk-based screening guidelines.

Dr. Otis Brawley, chief medical and scientific officer of the American Cancer Society, wrote a journal editorial accompanying the research.

Brawley stressed that people need to be educated about the benefits and risks of mammography when making screening decisions.

"I worry that the public perceives mammography as a better technology than it actually is," Brawley said. "Truth be told, it cannot avert all or even most breast cancer deaths."

Brawley concluded that breast screening guidelines tailored to the individual might recommend some women at very high risk get tested annually, some at intermediate risk get it every two years and those at normal risk start at a later age.

"Ultimately, the preferences of individual women, recognizing the potential for harm and benefit, should be respected."

All provincially organized screening programs in Canada encourage women aged 50 to 69 with no symptoms to have regular screening mammograms. The frequency depends on a woman's individual risk factors, such as family history.

Cancer specialists say the decrease in breast cancer mortality since 1985 is thanks to a combination of mammography screening, early detection from greater awareness and improvements in treatments.

The research was funded by the U.S. National Cancer Institute.