The mortality rate for U.S. women with breast cancer fell an estimated 58% from 1975 to 2019, according to research published in JAMA that credits the decline to advances in screening and treatments.

Nearly half (47%) of the reduction was attributed to earlier and more effective treatment of those with Stage 1, 2 or 3 breast cancer. (With staging, generally the lower the number, the less the cancer has spread.)

 A radiologist uses a magnifying glass to check mammograms for breast cancer in Los Angeles in 2010. Damian Dovarganes/Associated Press, file

In addition, about 25% of the drop was attributed to improved mammography screening and about 29% to better treatment of metastatic breast cancer, meaning cancer that has spread.

The findings used analysis of observational and clinical trial data from four models within the federally funded Cancer Intervention and Surveillance Modeling Network that track breast cancer screenings and treatments. Using modeling, the researchers were able to take into account changes in breast cancer incidence over time.

The 58% reduction figure represents “what the mortality would have been estimated to be in 2019 if no improvements [in screenings and treatments] had been made” in the 44 years examined, said Jennifer Caswell-Jin, the study’s lead author and an assistant professor of oncology at Stanford Medicine.

Without modeling, data shows that the mortality rate declined by 44% from 1975 to 2019, from 48 deaths per 100,000 women in 1975 to 27 per 100,000 women in 2019.

An editorial accompanying the research noted that, despite the “overall progress in reducing breast cancer mortality, reductions have not been equally distributed across all patient populations,” adding that rural, Black and uninsured patients are still “at greatest risk of dying from breast cancer.”

The American Cancer Society ranks breast cancer as the most common cancer among U.S. women (aside from skin cancers) and the second-leading cause of cancer deaths among women, following lung cancer.