Half of all women will receive at least one false positive mammogram per decade when undergoing annual breast cancer screenings via digital breast tomosynthesis.

Researchers at UC Davis Health found the risk was higher here, compared to when women undergo screening every other year over 10 years. They also say that repeated breast cancer screening with 3D mammography only modestly decreases the chance for a false positive, compared to standard digital 2D mammography.

False positives are common, with only 4.4% of the 12% of 2D screening mammograms recalled resulting in a cancer diagnosis. This means that false positives occur 0.5% of the time. “Despite the important benefit of screening mammography in reducing breast cancer mortality, it can lead to extra imaging and biopsy procedures, financial and opportunity costs and patient anxiety,” said senior author Diana Miglioretti, professor and division chief of biostatistics at the UC Davis Department of Public Health Sciences and UC Davis Comprehensive Cancer Center researcher.

The researchers assessed data from the Breast Cancer Surveillance Consortium on three million screening mammograms for 903,495 women, between 40 and 79, who were screened at 126 radiology facilities.

They found that 50% of women who were annually screened over 10 years would experience at least one false positive recall, compared to 56% screened every other year. In addition, 17% would receive a false positive short-interval follow-up recommendation, and 11% would receive a false positive biopsy recommendation, compared to 18% and 12%, respectively.

“We were surprised that the newer 3D technology in breast cancer screening does not substantially reduce the risk of having a false positive result after 10 years of screening; however, chances of false positives are much lower with repeated biennial versus annual screening,” said co-author Thao-Quyen Ho, a radiologist at the University Medical Center in Vietnam and a research fellow at UC Davis School of Medicine.

False positive findings were substantially lower among older patients than younger age groups and among women with entirely fatty tissue versus extremely dense breasts.

For short-interval follow-up recommendations, 17% who receive an annual 3D mammogram are estimated to have at least one false positive over 10 years, compared to 10% who undergo biennial screening. False positive benign recommendations are estimated to occur in 11% with annual 3D mammo and 7% with biennial screening.

The risk of a false positive was lower in 3D than 2D for all outcomes after 10 years of annual mammograms, and was the same for biennial screenings. No differences were found in short interval follow-up or biopsy recommendations for both types.

“Findings from our study highlight the importance of patient-provider discussions around personalized health. It is important to consider a patient’s preferences and risk factors when deciding on screening interval and modality,” said Michael Bissell, epidemiologist in the UC Davis Department of Public Health Sciences and co-first author of the study.

The findings were published in JAMA Network Open.

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