Orbital cancer: Historical trends in histological composition and cause-specific mortality based on SEER database analysis.

e18138 Background: Malignant orbital tumors are rare cancers encompassing a broad spectrum of lymphoid and epithelial histologies with variable clinical course and outcomes. In the United States, cancers of the eye and orbit are estimated to account for 3,140 new cases and 490 deaths annually. Data on orbital cancer all-cause mortality and competing causes of death remain limited. We set out to examine the histological distribution and causes of mortality among patients with primary malignant orbital cancers using the Surveillance, Epidemiology, and End Results (SEER) Research Plus database. Methods: Patients were identified using the International Classification of Diseases for Oncology, Third Edition (ICD-O-3) topography and morphology codes for orbital malignancies. The cohort included patients diagnosed with primary malignant orbital tumors between 2000 and 2022. Demographic, socioeconomic, tumor-related, and treatment variables were examined. Histologic subtypes were grouped into mucosa associated lymphoid tissue (MALT) lymphomas, non-MALT lymphomas, epithelial malignancies, and other orbital malignancies. Trends in histologic composition were evaluated. Causes of death were classified as orbital cancer-specific or non-cancer-related. Cancer-specific mortality was analyzed using cumulative incidence functions and Fine-Gray competing risk regression. Results: Among 2,154 patients, lymphoid malignancies predominated, including MALT lymphomas (48.6%), non-MALT lymphomas (29.6%), epithelial malignancies (11.8%) and other malignancies (10.1%). Over time, MALT lymphomas increased to half of the diagnoses after 2015, while non-MALT lymphomas declined and epithelial malignancies showed no significant trend. At the last follow-up in 2022, 59.1% of patients were alive. Orbital cancer-specific death accounted for 15.3% of mortality, while non-cancer causes, especially cardiovascular disease, represented an important competing risk, especially among indolent lymphoid histologies. Cancer-specific mortality varied by histology and was highest among epithelial malignancies. In multivariable Fine-Gray models, increasing age was independently associated with higher cancer-specific mortality across all histologies except epithelial malignancies. Lack of surgery was also associated with increased mortality among epithelial malignancies. Conclusions: This study highlights that malignant orbital tumors are characterized by shifting histologic patterns and heterogeneity in cancer-specific mortality. As survival improves for indolent lymphoid malignancies, non-cancer mortality becomes an increasingly important determinant of long-term outcomes. Histologic-specific risk analyses are essential to accurately characterize prognosis and optimize survivorship care in this patient population.