Mammography Screening Intervals and DCIS: What a New Study Reveals

Is it time to reevaluate mammography screening intervals?

In a recently published study in JAMA Network Open, researchers examined mammography screening intervals and six-year cumulative risks for ductal carcinoma in situ (DCIS) based upon data from 916,931 women (median baseline age of 54) who had a total of 2,320,016 annual mammograms, 681,983 biennial mammograms and 199,058 triennial mammograms between January 1, 2005 and December 31, 2020.

The study authors found that shorter intervals between mammography screening and age were associated with increased cumulative six-year risks of DCIS. For women between the ages of 40 to 49, the cumulative six-year DCIS risk for those undergoing annual mammography was 30 percent in comparison to 21 percent for biennial screening and 17 percent for triennial screening. For women between the ages of 70 and 74 who had annual mammograms, the researchers noted the six-year cumulative DCIS risk was 58 percent, 18 percent higher than those who had biennial screening (40 percent) and 25 percent higher than women who had triennial screening.

“Cumulative DCIS risk after 6 years of screening is substantially lower for women undergoing 2 triennial or 3 biennial screens compared with 6 annual screens,” wrote study co-author Karla Kerlikowske, M.D., who is affiliated with the Department of Medicine, the Department of Epidemiology and Biostatistics, and the General Internal Medicine Section in the Department of Veterans Affairs at the University of California, San Francisco, and colleagues.

Noting that DCIS comprises more than 30 percent of breast cancer cases diagnosed via mammography screening in the United States, the study authors said early detection of DCIS may lower the risk for the development of invasive breast cancer. However, pointing out that DCIS is considered a nonobligate precursor to invasive breast cancer, Kerlikowske and colleagues said the American Cancer Society and the U.S. Preventive Services Task Force have voiced concerns on potential overdiagnosis and treatment of DCIS.

(Editor’s note: For related content, see “What a New Mammography Study Reveals About Surveillance Imaging in Women Treated for Ductal Carcinoma In Situ” and “Interval Breast Cancer: What a New Mammography Study Reveals.”)

In line with findings from other studies, the study authors noted that a first-degree family history of breast cancer, breast density in younger women and a history of false positive mammography results in older women were strongly associated with DCIS diagnosis. Kerlikowske and colleagues suggested that their risk model may help clinicians balance mammography screening frequency needs and relevant risk factors for breast cancer.

“Our risk prediction model integrates screening interval and individual risk factors to estimate the probability of screen-detected DCIS,” noted Dr. Kerlikowske and colleagues. “These risk estimates can be used by policy makers in conjunction with estimates of other breast cancer screening outcomes (such as cumulative risk of false-positive mammography results and advanced cancer) when evaluating the balance of screening benefits and harms by screening interval.”

In regard to study limitations, the authors acknowledged they did not use nuclear grade to examine DCIS rates despite a reported correlation between nuclear grade and invasive breast cancer risk. The researchers also noted that a substantial number of reported mammography exams lacked information on BMI and menopausal status.