Breast cancer mortality rates in the U.S. in 2012 were roughly 50 percent lower than they would be without advanced screening and treatment, according to a new stimulation modeling study released online Jan. 9 by JAMA.

The question then left to readers is what contributed to this great reduction in mortality and more so created a positive effect in saving women's lives. The answer: advanced mammography screening and breast cancer treatment.

"Advances in screening and treatment are saving patients' lives, and [our research] quantifies just how much of a difference these advances are making," said lead author Sylvia Plevritis, PhD, professor of radiology at Stanford University's School of Medicine.

According to the study, researchers found that a combination of breast cancer screening and treatment reduced the number of deaths from breast cancer by 49 percent in 2012, compared to the number of deaths that would have otherwise occurred without advanced screening and treatment.

The American Cancer Society agreed with the findings. It stated in its annual report released early this month that female mortality caused by breast cancer fell 39 percent from 1989 to 2015.

According to Plevritis and her colleagues, one of the motives for the research was because most clinical trials don’t consider the effects of mammography screening and treatment when discussing mortality.

The researchers used six Cancer Intervention and Surveillance Network (CISNET) models using data from 2000 to 2012 from women ages 30 to 79 years old that compared age-adjusted, overall and ER/ERBB2-specific breast cancer mortality rates relative to the estimated mortality rate in the absence of screening and treatment or baseline rate.

The six models simulated mortality rates for intervention scenarios involving no screening or treatment, screening alone, treatment alone and screening and treatment combined.

The study concluded that in 2000, mammography screening and treatment contributed to a 37 percent reduction in overall breast cancer mortality as compared with the estimated baseline mortality rate (screening contributed to 44 percent and treatment contributed to 56 percent of the overall reduction rate).

In 2012, due to much advancement in both areas, mammography screening and treatment produced a 49 percent reduction in mortality.

"[Our] results support findings that advances in mammography continue to contribute to reducing breast cancer mortality," Plevritis and her colleagues concluded. "It will be important to update the analysis when there is sufficient evidence about the benefits of tomosynthesis or other emerging screening approaches."