Annual mammograms for women beginning at age 40 prevent the greatest number of breast cancer deaths, according a new study from Weill Cornell Medicine investigators. The findings, published Aug. 21 in Cancer, may help settle an ongoing debate about when and how often women should undergo screening mammography.

Using breast-cancer-specific computer models from the Cancer Intervention and Surveillance Modeling Network (CISNET) of the National Cancer Institute, the research team compared three prevailing mammography recommendations from the American College of Radiology/Society of Breast Imaging (ACR/SBI), the American Cancer Society (ACS) and the United States Preventive Services Task Force (USPSTF). The recommendations include annual screenings starting at age 40, annual screenings from ages 45 to 54 followed by biennial screenings from ages 55 to 79, and biennial screenings from ages 50 to 74, respectively.

“A lot of press focuses on the risks of screening, which are not unique to mammography, but not the benefits,” said first author Dr. Elizabeth Arleo, an associate professor of radiology at Weill Cornell Medicine and a radiologist at NewYork-Presbyterian/Weill Cornell Medical Center. “This is an important study with a bottom line that annual screening starting at age 40 saves the most lives.”

The CISNET breast cancer models calculate screening mammography benefits in terms of averted breast cancer deaths and years of life gained by screening per 1,000 women; risks focus on the number of screening mammograms performed, benign recalls and benign biopsies. CISNET used data from a single-year cohort of women in the U.S. born in either 1960 or 1970 depending on the CISNET model.

Arleo and her team used both the 2009 and 2016 models to see how different screening guidelines would affect breast cancer specific mortality. The models showed that the ACR/SBI’s recommendation of annual screenings beginning at age 40 led to a 39.6 percent reduction of death – compared with women who did not undergo screening – the greatest reduction of all recommendations. In comparison, screening recommendations from the ACS and USPSTF resulted in 30.8 percent and 23 to 27 percent reduction, respectively.

Arleo said the results were “predictable and consistent” with diverse data.

Health organizations have been providing conflicting guidelines about when women should start screening for breast cancer with much of the debate focusing on the value of mammograms in the face of false positives and over-diagnosis.

“Health care costs are steep,” she said. “While some may consider cutting back on screening to lower these costs, our research shows that, in order to save the most lives from breast cancer deaths, annual screening mammography should start at age 40. We need a national consensus promoting this recommendation.”

Molly Schulson is a freelance writer for Weill Cornell Medicine.