Real-world treatment patterns and survival outcomes in splenic marginal zone lymphoma: A SEER analysis (2000-2022).

e19096 Background: Splenic marginal zone lymphoma (SMZL) is a rare, indolent B-cell non-Hodgkin lymphoma with heterogeneous clinical behavior and evolving treatment paradigms. Population-level data on management patterns and long-term outcomes remain limited. We analyzed trends in treatment utilization and survival outcomes for patients with SMZL using a large, nationally representative cohort. Methods: Patients diagnosed with SMZL between 2000-2022 were identified from the SEER database. Demographic, clinical, and treatment variables, including age, sex, race/ethnicity, grade, Ann Arbor stage, splenectomy, chemotherapy, and survival outcomes were extracted. Treatment eras were categorized as 2000-2007, 2008-2015, and 2016-2022. Kaplan–Meier methods estimated overall survival (OS) and cancer-specific survival (CSS). Cox proportional hazards models evaluated prognostic factors. Results: A total of 2,641 patients were included (median age 67 years; 45% male; 89% white; 91% non-Hispanic). Advanced-stage disease (III–IV) was present in 42.8%. Observation was the most common treatment strategy (48.3%), followed by chemotherapy (21.3%), splenectomy (17.9%), and combined therapy (4.5%). Treatment patterns varied significantly across eras (p < 0.001), with declining splenectomy use and increased adoption of systemic therapy. Median OS was 134 months. OS rates at 1, 5, and 10 years were 91.4%, 74.0%, and 54.6%, respectively. The 10-year CSS was 76.3%, with a lymphoma-specific mortality rate of 18.7%. In multivariable analysis, age ≥75 years was strongly associated with inferior OS (HR 11.01, p <0.001), as were male sex (HR 1.18; p <0.05) and stage III disease (HR 1.76; p<0.05). Diagnosis in the 2008-2015 era was associated with improved survival compared with 2000–2007 (HR 0.76, p < 0.001). Combined splenectomy + chemotherapy was associated with increased mortality risk (HR 1.63, p < 0.001). Splenectomy showed a modest unadjusted OS benefit (p = 0.011), but this was not significant after adjustment (p = 0.788). Conclusions: In our study, SMZL demonstrated excellent long-term disease-specific survival but substantial age-related mortality. Treatment patterns evolved significantly over two decades, with decreasing reliance on splenectomy. Advanced age, male sex, and higher stage were independent predictors of worse outcomes. Combined splenectomy + chemotherapy was associated with inferior survival, underscoring the need for careful treatment selection.