SAT-331 Survival Trends and Prognostic Factors in Primary Thyroid Lymphoma: Insights from SEER Database Analysis

Abstract Disclosure: F. Toloza Bonilla: None. S. Gubbi: None. J. Klubo-Gwiezdzinska: None. Background: Primary thyroid lymphoma (PTL) is a rare malignancy, accounting for less than 5% of thyroid cancers and approximately 2.5% of lymphomas. Historically, surgery and radiation were the primary treatments, but these approaches were associated with poor outcomes. While the introduction of combined chemotherapy with radiation has improved survival, the survival trends and prognostic factors for PTL following the adoption of this therapy remain under explored. Methods: We conducted a retrospective cohort study using SEER database records of PTL patients aged 20 years or older diagnosed between 1975 and 2021. Demographic and clinical data were analyzed, including age, sex, race, lymphoma subtype, stage, and treatments received. Kaplan-Meier analysis was used to estimate overall survival (OS) and disease-specific survival (DSS), while Cox proportional hazards models identified predictors of mortality. Treatment groups were categorized as chemotherapy and radiation therapy with or without surgery, chemotherapy alone, radiation therapy alone, or no therapy. Results: Among the 2,465 patients, 76% were diagnosed between 2001 and 2021. The mean age at diagnosis was 66 years (standard deviation (SD): 13.9 years), with 69.9% female and 88.8% White. Diffuse large B-cell lymphoma (DL-BCL) was the most common subtype (62.5%). Most patients (41%) presented with localized disease. The median OS was 150 months (95% CI: 140-160), with 1-, 5-, and 10-year OS rates of 84.9%, 72.9%, and 57.7%, respectively. DSS rates were 89.1%, 83.7%, and 80.5%. Combined chemotherapy and radiation therapy resulted in the highest 10-year DSS (86.6%), followed by chemotherapy alone (77.2%), radiation therapy alone (77%), and no treatment (68.2%). Survival rates were significantly higher in patients diagnosed between 2001 and 2021 compared to earlier periods (10-year OS rate: 61.9% vs. 47%, p-value < 0.01; 10-year DSS rate: 83.3% vs. 72.5%, p-value < 0.01). Predictors of worse PTL-related mortality included older age (≥70 years), advanced stage, and lack of treatment, while combined chemotherapy and radiation therapy showed the greatest reduction in mortality risk (Hazard ratio (HR) = 0.34; 95% CI 0.24-0.46). Conclusion: PTL survival outcomes have significantly improved over recent decades due to advancements in treatment strategies, particularly combined chemotherapy and radiation therapy. Early diagnosis and appropriate treatment remain critical for improving prognosis, emphasizing the need for continued research into optimal therapeutic approaches for PTL. Presentation: Saturday, July 12, 2025