Race, sex, and survival disparities in mycosis fungoides and Sézary syndrome: A SEER8 database analysis (1975–2021).

e19056 Background: Cutaneous T-cell lymphoma (CTCL), including mycosis fungoides (MF) and Sézary syndrome (SS), exhibits survival disparities by race and sex. Although delayed diagnosis has been implicated in poorer outcomes among Black patients, earlier onset and worse survival suggests additional biological and systemic contributors. This study aimed to analyze epidemiological trends in overall survival (OS) and disease-specific survival (DSS) among MF and SS patients. Methods: The Surveillance, Epidemiology, and End Results (SEER) 8 registries database (1975–2021) was analyzed to identify MF and SS cases. Outcomes, including OS and DSS, were stratified by race and sex, and survival trends were evaluated. Kaplan-Meier methods were used to calculate age-adjusted OS and DSS, stratified by race (Non-Hispanic White [NHW], Non-Hispanic Black [NHB], Hispanic) and sex. SEER 22 database (2000-2021) was used for further validation. Statistical significance was defined as p<0.05. Results: 5330 MF and 193 SS patients were analyzed. Median age at diagnosis for MF and SS were 69 and 60 years. MF and SS were more common in males (MF: 59.5% male vs. 40.5% female; SS: 60.6% male vs. 39.4% female) and White (MF: 76.3% White vs. 23.7% other races; SS: 80.8% White vs. 19.2% other races). For MF, Black patients peaked in the 41–60 age range, while White patients peaked in the 61–70 age range. In SS, Black patients were more evenly distributed across midlife and older groups (31–80), while White patients peaked in the 71–80 range. For MF, the 5-year OS was 74.1% (95% CI: 72.5%–75.5%) and the DSS was 87.2% (95% CI: 85.9%–88.4%). NHW patients had better 5-year OS and DSS compared to NHB patients (OS: 74.6% [95% CI: 72.8%–76.3%] vs. 61.8% [95% CI: 55.2%–67.7%]; DSS: 86.9% [95% CI: 85.3%-88.3%] vs. 78.9% [95% CI: 71.5%-84.5%], respectively). Females had higher OS but similar DSS to males. For SS, the 5-year OS was 42.1% (95% CI: 33.6%–50.2%) and DSS was 53.4% (95% CI: 43.9%–62.1%). NHB males had the poorest outcomes compared to NHW male patients, with a 5-year OS of 25.9% vs. 39.6% and a 5-year DSS of 29.6% vs 51.4%. With SEER 22, we further confirmed significantly lower OS and DSS in Black male patients, especially those over 60. For MF, DSS improved after the late 1990s, reflecting advances like interferon and Bexarotene, with the most notable gains in 5-year DSS observed after 2010. For SS, OS and DSS have significantly increased since 2010, likely due to introduction of targeted therapies like mogamulizumab. Conclusions: This study highlights racial and sex-based survival disparities in MF and SS, with NHB males facing worse outcomes. We hypothesize that variations in the genetic landscape across races contribute to outcome differences. Our future research will incorporate institutional data and cancer somatic mutation data to explore the causes and develop targeted interventions to reduce disparities in underserved populations.