Current screening, treatments reduced breast cancer mortality by 58% since 1975

Key takeaways:

• U.S. breast cancer mortality rates dropped by 58% from 1975 to 2019.
• Reductions were associated with metastatic breast cancer treatment, stage I to III treatment and mammography screening.

Breast cancer screening and treatments in 2019 were both associated with more than 50% reduction in U.S. breast cancer mortality compared with interventions utilized over 4 decades ago, according to analysis results published in JAMA.

The Cancer Intervention and Surveillance Modeling Network (CISNET) was developed to create simulation models to quantify associations between screening mammography and breast cancer stage I to III therapy with reductions in breast cancer mortality.

“Since 2000, results of new randomized clinical trials for metastatic breast cancer demonstrated further improved patient outcomes, yet the consequences of these changes have not been quantified,” Jennifer L. Caswell-Jin, MD, assistant professor of medicine (oncology) at Stanford University School of Medicine, and colleagues wrote. “Therefore, the CISNET models were revised to specifically evaluate how recent treatments of metastatic breast cancer may have been associated with reduced breast cancer mortality in the U.S.”

Caswell-Jin and colleagues used aggregated observational and clinical trial data on the extent and effects of breast cancer screening and treatment and simulated U.S. breast cancer mortality rates using CISNET. Researchers simulated models for death due to breast cancer, overall and by estrogen receptor and ERBB2 status among women aged 30 to 79 years in the U.S. from 1975 to 2019.

In the U.S., the breast cancer mortality rate was 48 per 100,000 women in 1975 and dropped to 27 per 100,000 women in 2019. The combination of breast cancer screening, stage I to III treatment and metastatic treatment was associated with a 58% reduction in breast cancer mortality in 2019.

Overall, 29% of the reduction was associated with metastatic breast cancer treatment, 47% with stage I to III breast cancer treatment and 25% with mammography screening.

Based on the CISNET simulation models, the greatest survival change following metastatic recurrence occurred from 2000 to 2019, from 1.9 years to 3.2 years. In addition, in 2019, median survival for women with estrogen receptor-positive/ERBB2-positive breast cancer improved by 2.5 years, and median survival for women with estrogen receptor-negative/ERBB2-negative breast cancer improved by 0.5 years.

“The updated CISNET models reported here describe the association of treatments for metastatic breast cancer with population-level mortality for the period 1975-2019,” the researchers wrote. “The results suggest that advances in the treatment of metastatic breast cancer were associated with lower rates of breast cancer mortality in the U.S.”