Screening, Improved Metastatic Treatments Responsible For Substantial Decline in Breast Cancer Mortality Rate

In the United States, breast cancer mortality declined 58% between 1975 and 2019. The decrease was, in part, due to the combined impact of screening and improved stage I to stage III and metastatic breast cancer treatments, according to a recent study.

In their study, researchers used data from observational and clinical trials, aggregated to develop four Cancer Intervention and Surveillance Modeling Network (CISNET) models. These models simulated breast cancer mortality rates among women aged 30 to 79 in the United States from 1975 to 2019. Previous studies used CISNET modeling based on simulation models, which showed improvements in breast cancer screening and therapy for stage I to III breast cancer between 1975 and 2012. This study also examines metastatic treatments and extends that timeline out further to 2019.

The study results show a substantial decline in the age-adjusted breast cancer mortality rate, from 48 of 100,000 women in 1975 to 27 of 100,000 women in 2019. In 2019, the combined impact of screening, stage I to III treatment, and metastatic treatment was associated with a 58% reduction in breast cancer mortality. The CISNET models suggest that treatment for metastatic breast cancer contributed 29% (model range, 19%-33%) to this reduction, treatment for stage I to III breast cancer contributed 47% (model range, 35%-60%), and mammography screening contributed 25% (model range, 21%-33%).

Interestingly, the simulations indicate that the most significant improvement occurred between 2000 and 2019, with the median survival increasing from 1.9 years to 3.2 years. But the survival time varied based on estrogen status. For example, participants with estrogen receptor-positive and HER2-positive breast cancer had an average increase in survival time of 2.5 years between 2000 to 2019. Participants with estrogen receptor-negative and HER2-negative breast cancer lived about 0.5 years longer during that same timeframe.

This study had several limitations, including the researcher’s assumptions about when data was unavailable. Additionally, the model did not incorporate patient disparities or treatment costs, all of which may impact breast cancer mortality.

“The results suggest that advances in the treatment of metastatic breast cancer were associated with lower rates of breast cancer mortality in the United States,” the authors concluded.

Reference:
Caswell-Jin JL, Sun LP, Munoz D, et al. Analysis of breast cancer mortality in the US-1975 to 2019. JAMA. 2024;331(3):233-241. doi:10.1001/jama.2023.25881