Radiation-induced breast cancer risk from digital mammography is low for the majority of women, but risk is higher in women with large breasts, who received 2.3 times more radiation and required more views per examination to image as much of the breast as possible compared to those with small or average-sized breasts.
The study also found that screening every two years instead of annually, and beginning at age 50 instead of 40 or 45, lowers the likelihood of radiation-induced breast cancer in all women. The findings, led by Rebecca Hubbard, PhD, an associate professor of Biostatistics in Biostatistics and Epidemiology in the Perelman School of Medicine at the University of Pennsylvania, appear online this week in Annals of Internal Medicine.
In eight screening strategies estimated using two models, the group simulated the lifetime risk of women developing radiation-induced breast cancer from digital screening mammography and dying from the disease compared to the number of deaths averted through early detection.
The group found that screening 100,000 women, ages 50 to 74, every two years, prevented 627 deaths. The radiation exposure from these screening exams, and any subsequent diagnostic work-ups, caused 27 breast cancer cases and 4 breast cancer deaths. Although screening 100,000 women annually from 40 to 74 years prevented 968 deaths, it also raised cancer risk five-fold, causing 100 additional radiation-induced breast cancers and 12 additional breast cancer deaths compared with screening every two years from age 50 to 74.
Recommendations released earlier this week by the U.S. Preventive Services Task Force, an independent panel appointed by the federal government, echo the study's finding that women between the ages of 50 and 74 should be screened once every two years for breast cancer.
"Choosing a screening schedule that reduces harms while maintaining the benefits of more frequent screening makes screening mammography safer for all women," Hubbard said. "As our understanding of the effects of individual characteristics on harms and benefits of mammography grows, we can more effectively tailor screening strategies to minimize harms and save more lives."
While not explicitly reviewed in the research, the findings suggest risk is also higher in those with breast implants, which require twice as many views during mammography, and/or denser breasts which require additional evaluations resulting in more radiation exposure.
The study also noted that obtaining fewer mammograms would also result in fewer false positives, which can prevent radiation exposure from possibly unneeded follow-up diagnostic mammograms.
Although women with large breasts are at greater risk, larger detectors can image women in this population with fewer views and less radiation. In addition, 3-D tomosynthesis may also lessen exposure from diagnostic evaluations if early evidence of reduced false-positives holds up in larger studies.