Epidemiologic Trends in Secondary Malignant Neoplasms of the Liver in the United States: A 25-Year National Study

Background Secondary malignant neoplasms of the liver (SMNL) are more common than primary liver cancers but remain understudied. This study provides the first nationwide analysis of SMNL mortality trends and disparities in the US. Methods This study analyzed SMNL-related (ICD-10: C78.7) CDC WONDER mortality data (1999–2023), and US Cancer Statistics incidence data for adults ≥ 45 years, stratified by demographics, geography, and primary site. Age-adjusted mortality and incidence rates (AAMRs, AAIRs) and crude mortality rates (CMRs) were reported per 100,000 population. Temporal trends were analyzed using Joinpoint regression. Results SMNL-related AAMR rose from 23.8 (1999) to 25.1 (2023). Males accounted for 51.3% of the 597,332 deaths and had higher AAMRs than females throughout. Lung (25.6%) and colon (24.6%) cancers were the leading primary sites causing SMNL-related deaths. AAIRs and AAMRs (irrespective of metastasis) declined for most primary cancers. CMRs progressively increased across each successive 10-year age group. Non-Hispanic (NH) Blacks had the highest AAMR but with a declining trend, while NH Whites saw a significant increase. West’s AAMRs showed the biggest increase. Rural areas consistently had higher AAMRs. Conclusions SMNL mortality is rising among older US adults, with disparities. Improved primary cancer survival extends the window for metastatic progression, highlighting the need for better detection and management.