47 A comprehensive study by the Cancer Intervention and Surveillance Modeling Network (CISNET) has shown a remarkable 58% reduction in breast cancer mortality in the US from 1975–2019. The study, published in the Journal of the American Medical Association (JAMA), attributes this decline to improvements in screening, treatment for stage I to III breast cancer, and treatment for metastatic breast cancer. The study employed four sophisticated simulation models to analyse age-adjusted breast cancer mortality rates among women aged 30 to 79. The models replicated real-world data, estimating that, without any new interventions, the breast cancer mortality rate in 2019 would have been 64 deaths per 100,000 women. But due to the implemented interventions, this rate fell to 27 deaths per 100,000 women. The study found that the reduction in breast cancer mortality can be largely attributed to three key factors: Stage 1– 3 breast cancer treatment. This accounted for the largest portion of the mortality reduction, approximately 47%. The treatments included surgery, radiation, and systemic therapies, which have significantly evolved over the past few decades. Metastatic breast cancer treatment. This contributed to 29% of the reduction. Advances in treatments for metastatic breast cancer, particularly new drug approvals and targeted therapies, have improved survival rates even in advanced stages of the disease. Screening mammography. Screening alone was associated with a 25% reduction in mortality. Early detection through mammography has allowed for earlier and more effective treatment interventions. The study also highlighted improvements in median survival rates following metastatic recurrence. Between 2000 and 2019, median survival for breast cancer patients increased from 1.9 years to 3.2 years. This improvement was most notable in patients with oestrogen receptor-positive (ER+) and ERBB2-positive (formerly HER2) breast cancer, who saw an increase in median survival of up to 2.5 years. Patients with ER-negative and ERBB2-negative breast cancer experienced more modest gains, with an improvement of 0.5 years in median survival. The study noted that the US Food and Drug Administration (FDA) approved 30 drugs for breast cancer treatment between 2010 and 2020, with the majority targeting metastatic disease. These new treatments have been pivotal in enhancing survival rates and reducing mortality. Additionally, the study pointed out the critical role of ongoing clinical trials in continuously improving treatment protocols and outcomes. The study found that the benefits of screening and treatment varied by cancer subtype. For instance, the mortality reduction was greatest for ER+/ERBB2+ cancers, while ER−/ERBB2− cancers saw the least reduction. This disparity underscores the need for continued research and development of targeted therapies for less responsive cancer subtypes. Despite the significant findings, the study acknowledged several limitations. The models did not account for disparities in treatment access and outcomes based on age, race, and ethnicity. Moreover, the costs associated with treatments were not included in the analysis. Future research should aim to address these gaps and explore the socio-economic factors influencing breast cancer mortality.