Repeated Mammography Screening May Increase Cancer Risk

Women with large breasts who undergo repeated screening mammography may be at higher risk for radiation-induced breast cancer and breast cancer death, according to a study published in the Annals of Internal Medicine.

Researchers from the United States and the Netherlands sought to determine radiation-induced breast cancer incidence and mortality in relation to repeated exposure to screening and diagnostic mammography and dose variation.

The researchers projected that annual digital mammographic screening of 100,000 women (aged 40 to 74) would induce 125 cases of breast cancer, and that there would be 16 deaths, relative to 968 breast cancer deaths that would have been averted by early detection from screening.

“Women exposed at the 95th percentile were projected to develop 246 cases of radiation-induced breast cancer leading to 32 deaths per 100,000 women,” the authors wrote.

Women with large breasts may require extra views for complete examination and this made up about8% of the population. These women were projected to have greater radiation-induced breast cancer risk of 266 cancer cases and 35 deaths per 100,000 women, compared with other women, who were projected to have 113 cancer cases and 15 deaths per 100,000 women. The researchers found that the risk for radiation-induced cancer was reduced five-fold when biennial screening began at age 50.[[{"type":"media","view_mode":"media_crop","fid":"45224","attributes":{"alt":"mammography","class":"media-image media-image-right","id":"media_crop_280844085558","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"5135","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 114px; width: 171px; border-width: 0px; border-style: solid; margin: 1px; float: right;","title":"©zlikovec/Shutterstock.com","typeof":"foaf:Image"}}]]

“[W]e estimate that the number of breast cancer cases induced by screening is probably very small, even for women with the greatest radiation exposures,” they wrote. “However, relative to the number of breast cancer deaths averted with screening, radiation-induced breast cancer incidence is not trivial. Most concerning are numbers projected for annual screening and screening before age 50 years of women with large breasts requiring extra views for complete examination, who have more than twice the risk for radiation-induced breast cancer as women with small or average-sized breasts.”

The authors concluded that both breast cancer incidence and mortality resulting from screening by digital mammography were affected by dose variability, resultant diagnostic work-up, initiation age, and screening frequency, possibly affecting women with large breasts more than other women. They encouraged radiologists to limit the number of views to as few as possible, particularly for women with large breasts.