Deaths mentioning lung metastases reached their highest recorded US rate in 2024

Abstract Background. Metastatic disease contributes substantially to cancer mortality, and the lung is a common site of distant spread. National mortality patterns involving secondary malignant neoplasm of the lung remain poorly described. Methods. We conducted a serial cross-sectional analysis of CDC WONDER Multiple Cause of Death data for US adults aged ≥25 years from 1999 through 2024 with ICD-10 code C78.0 recorded anywhere on the death certificate. Age-adjusted mortality rates (AAMRs) per 100,000 population were standardized to the 2000 US population. Trends were evaluated using joinpoint regression from 2000, with 1999 retained in sensitivity analysis. Eight prespecified sensitivity analyses included normalization to total cancer mortality and exclusion of deaths co-mentioning primary lung cancer. Results. C78.0 was recorded in 523,763 deaths. The AAMR declined from 11.33 per 100,000 in 1999 to 7.22 in 2008, then increased to 11.38 in 2024, the highest observed rate and 17.5% above the 2000 level (AAPC, +0.75%/year; 95% CI, 0.05 to 1.46). Relative increases were 70.5% among adults aged 25–34 years and 62.5% among those aged ≥85 years, compared with 4.3%–17.6% among those aged 45–84 years; only the oldest group showed a statistically supported increase. The male-to-female rate ratio narrowed from 1.43 to 1.22. Non-Hispanic Black adults had the highest rate in 1999 but no clear net change (AAPC, −0.15%/year; 95% CI, −0.81 to 0.52). Non-Hispanic White mortality exceeded that of non-Hispanic Black adults in 2019; post-2020 comparisons require caution because of classification changes. The West shifted from the lowest- to highest-mortality census region. C78.0 mentions per 1,000 cancer deaths increased 66.3%, while overall cancer mortality declined 30.1%. Conclusions. Mortality involving secondary malignant neoplasm of the lung increased after 2008 and reached its highest observed level in 2024. The increase relative to total cancer mortality provides additional context but does not explain the trend. Changes in survival, metastatic disease burden, detection, or death-certificate documentation may have contributed. These findings are descriptive and do not establish that demographic or geographic characteristics caused the mortality differences. Individual-level linkage with incidence and clinical data is needed to examine these possibilities.