Sézary Syndrome: Survival Trends, Racial Disparities, and Limited Prognostic Value of Routine Registry Variables.

INTRODUCTION: Sézary syndrome (SS) is a rare leukemic cutaneous T-cell lymphoma with limited contemporary population-level outcome data. METHODS: Using SEER-22, we identified 403 adults with first primary SS diagnosed from 2000-2021 and evaluated survival, disparities, and prognostic modeling. RESULTS: Median overall survival (OS) was 48 months; 5-year OS was 42.7%. Survival improved from 39.5 months in 2000-2010 to 56.0 months in 2011-2021. Black patients were diagnosed younger and had worse adjusted mortality than White patients. Machine-learning and conventional models showed limited discrimination. CONCLUSION: SS remains highly lethal, with persistent racial disparities and limited prognostic value of routine registry variables. TRIAL REGISTRATION: The authors have confirmed clinical trial registration is not needed for this submission.