Secondary hematologic malignancy mortality in older survivors of gastrointestinal cancer.

e18611 Background: Improved survival following gastrointestinal (GI) cancers has increased the population at risk for second hematological malignancies (SHMs), including leukemia, lymphoma, and myelodysplastic syndromes. However, demographic, geographic, and urban–rural disparities related to SHMs among older GI cancer survivors at the national level remain insufficiently described. Methods: We conducted a nationwide cross-sectional mortality analysis using the CDC-WONDER Multiple Cause-of-Death database from 1999 to 2023. Deaths among individuals aged ≥65 years with both GI malignancies (ICD-10 C15–C26) and SHMs (ICD-10 C81–C96) listed on death certificates were included. Crude mortality rates (CMRs) and age-adjusted mortality rates (AAMRs) per 1,000,000 population were calculated using the 2000 U.S. standard population. Temporal trends were evaluated using Joinpoint regression to estimate annual percent change (APC) and average annual percent change (AAPC) with 95% CIs. Results: A total of 22,668 SHM-related deaths among older adults with GI malignancies were identified. The overall AAMR increased from 21.88 in 1999 to 25.55 in 2023. Nationally, mortality declined from 1999 to 2018, followed by a significant rise from 2017 to 2023 (APC 5.49; 95% CI 3.63–8.61). Males had a substantially higher average AAMR than females (31.07; 95% CI 28.40–33.74 vs. 14.10; 95% CI 12.65–15.58). Among males, AAMRs declined till 2017, before increasing sharply from 2017 to 2023 (APC 5.63; 95% CI 3.57–9.03). Females showed a decline till 2015, followed by an increase from 2015 to 2023 (APC 3.58; 95% CI 2.15–5.78). Age-stratified analyses demonstrated rising mortality with advancing age: CMRs were lowest among those aged 65–74 years (10.56; 95% CI 9.25–11.88) and highest among those aged ≥85 years (45.71; 95% CI 40.03–51.39). Recent increases were observed across all age groups, most pronounced in adults aged ≥85 years (APC 6.88; 95% CI 3.51–14.55 from 2017–2023). Non-Hispanic White individuals had the highest average AAMR (22.35; 95% CI 20.76–23.93), followed by Black or African American individuals (18.84; 95% CI 14.51–23.98), with both groups exhibiting significant post-2016 increases. Regionally, the Midwest recorded the highest average AAMR (25.65; 95% CI 22.42–28.88). Non-metropolitan areas consistently showed higher mortality than metropolitan areas (23.37; 95% CI 19.89–26.85 vs. 19.98; 95% CI 18.46–21.50). Conclusions: SHM-related mortality among older adults with GI malignancies has risen significantly in recent years, following nearly two decades of decline. Marked disparities by sex, age, race/ethnicity, geography, and urbanization persist. These findings highlight an urgent need for enhanced survivorship surveillance, equitable access to oncology care, and targeted public health interventions to address the growing and uneven burden of secondary hematological malignancies.