Metastatic breast cancer-related mortality with thoracic involvement among U.S. adults aged ≥ 25 years: A retrospective CDC WONDER analysis from 1999 to 2024.

Abstract

e13094 Background: Breast cancer is one of the most commonly diagnosed malignancies and a leading cause of cancer-related mortality in the United States, with metastatic disease responsible for most deaths. The disease commonly spreads via hematogenous and lymphatic pathways to the thoracic compartment, particularly the lungs and pleura. Thoracic involvement is associated with severe, often fatal complications including malignant pleural effusion, lymphangitic carcinomatosis, and respiratory failure. However, long-term national mortality trends related to thoracic involvement in metastatic breast cancer remain poorly defined. This study evaluates long-term national mortality trends associated with thoracic involvement in metastatic breast cancer among U.S. adults aged ≥25 years from 1999 to 2024. Methods: We conducted a retrospective analysis using the CDC WONDER multiple cause-of-death database from 1999 to 2024. Deaths among adults aged ≥25 years with breast carcinoma (ICD-10: C50) and concurrent lung or pleural metastases (C78.0, C78.2) were identified. Age-adjusted mortality rates (AAMRs) per 100,000 population were calculated and stratified by age, sex, race/ethnicity, U.S. Census region, and urbanization status. Temporal trends were assessed using Joinpoint regression to estimate annual percent change (APC) and average annual percent change (AAPC). Results: From 1999 to 2024, a total of 79,749 deaths were attributed to metastatic breast cancer with thoracic involvement. Overall mortality showed a non-significant decline trend (AAPC: −0.39) with temporal variability. Females had markedly higher mortality than males (AAMR: 2.39 vs 0.03), with a significant decline from 1999 to 2008 (APC: −4.23). Among age groups, adults aged ≥65 years bore the highest mortality burden, with a significant increase between 2013 and 2017 (APC: 5.47). By race/ethnicity, Non-Hispanic Asian individuals demonstrated an overall increasing trend (AAPC: 1.20), with a sharp rise from 2013 to 2018 (APC: 8.08). Regionally, mortality declined across all U.S. Census regions, most prominently in the Northeast (AAPC: −1.61). Both metropolitan and non-metropolitan areas showed declining trends, with the steepest reduction in metropolitan areas from 1999 to 2008 (APC: −4.23). Conclusions: Mortality related to thoracic involvement in metastatic breast cancer shows substantial temporal and demographic heterogeneity in the United States. Early declines have plateaued, with recent increases observed after 2017, particularly among older adults and non-Hispanic Asian females. These findings suggest a potential reversal of prior gains and highlight persistent geo-demographic disparities, emphasizing the need for improved surveillance, earlier detection, and equitable multidisciplinary care.