Trends and Disparities in Secondary Malignant Neoplasms of the Bone in the United States: The WONDER Study

Background/Objectives: Secondary malignant neoplasms of the bone are a major concern for cancer patients, with significant morbidity and mortality despite advancements in cancer care. The current literature reports demographic variability, but population-level trends and survivor-specific risk factors remain poorly characterized for bone metastasis. This study aims to provide a comprehensive temporal analysis of the trends and disparities of secondary malignant neoplasms of the bone. Methods: Deidentified death certificate data from the United States as reported in the CDC WONDER database (1999–2023) were analyzed for secondary malignant bone neoplasms (ICD-10 C79.5). Age-adjusted mortality rates per 100,000 were calculated and stratified by gender, age, and race. Temporal trends were assessed using Joinpoint Regression, yielding APCs, AAPCs, and 95% CIs. Results: Between 1999 and 2023, there were 424,811 deaths in U.S. adults over the age of 25 years related to secondary malignant bone neoplasms. The overall age-adjusted mortality rate (AAMR) increased from 5.77 (95% CI 5.67 to 5.87) in 1999 to 11.92 (95% CI 11.79 to 12.05) in 2023. The average annual percentage change (AAPC) over this period was 3.28 (95% CI 2.63 to 3.94). From 1999 to 2009, mortality decreased with an annual percentage change (APC) in AAMR of −3.62 (95% CI −4.92 to −2.30), followed by a sharp increase in mortality between 2009 and 2023 with an APC of 8.52 (95% CI 7.83 to 9.19). Certain populations had greater increases in AAMR over the study period. The population aged 85 years and older had the largest increase in mortality from secondary malignant bone neoplasms with an AAPC of 4.77 (95% CI 3.38 to 4.77). Over the study period, Black individuals had an overall AAPC of 1.53 (95% CI 0.11 to 2.97), White individuals had an AAPC of 2.60 (95% CI 1.61 to 3.60), and Asian or Pacific Islanders had an AAPC of 3.74 (95% CI 1.17 to 6.38). Rural areas had overall higher AAMRs compared to urban areas, with an AAPC of 2.27 (95% CI 1.52 to 3.02). Conclusions: Overall, AAMR increased from 1999 to 2023, though there was a period of decreasing AAMR from 1999 to 2009. We suggest that due to increased rates of screening, it is possible that rates of secondary metastases of the bone have been constant over the years, but they were not diagnosed, leading to a false increase in AAMR. Mortality rates were highest in Black individuals in our study, possibly pointing towards discrepancies in cancer screening and treatment between races. Additionally, the AAMR was higher in rural than in urban areas, which we hypothesize may be due to limited access to treatment, such as surgery. Our study was limited by its nature as a database study, but future studies should focus on the prevention of primary malignancies and minimizing risk factors for the development of secondary malignancies.