Identifying Racial and Ethnic Disparities in Patients Diagnosed with Mycosis Fungoides/sezary Syndrome in the United States: A Contemporary SEER Analysis.

7544 Background: Mycosis fungoides (MF) and Sezary syndrome (SS) are rare cutaneous T-cell lymphomas. In this study, we compare demographics, treatment, and survival patterns in Hispanic (HI) vs. Non-Hispanic (NH) patients diagnosed with MF and SS. Methods: Data were analyzed on MF and SS patients in the US reported to SEER 18 database between 2000 and 2018. SEER 18 contains the most comprehensive population-based cancer information in the US, covering approximately 27% of the total US population, and up to 36% of HI. Racial groups analyzed included NH whites, HI whites, blacks, and Asians/Pacific Islanders. Patient characteristics, age-adjusted incidence rate, and survival rate were compared across ethnic groups, HI vs NH. Stratification by age, gender, and stage at diagnosis were considered. Kaplan-Meier and Cox regression analyses were used to compare overall survival (OS) between HI and NH. Multivariate analysis and propensity score matching were performed with adjustment for age, stage, and B-symptoms. Results: 8578 patients with MF and 275 patients with SS were identified. Of patients with MF, 11% were HI and 89% were NH; of patients with SS, 12% were HI and 88% were NH. In NH patients with MF, most patients were male (58%); for HI patients with MF, a male predominance was not observed (p < 0.001). In patients with SS, most patients were male in both NH and HI (56% NH, 56% HI; p = 0.989). In both MF and SS, HI were diagnosed at younger ages compared to NH, 49 y.o vs 60 y.o (p < 0.001) and 59 y.o vs 71 y.o (p = 0.009) respectively. Most HI and NH with MF and SS did not receive radiotherapy (91% of NH and 92% of HI for MF; 92% of NH and 91% of HI for SS; p values 0.166 and 0.760, respectively). On survival analysis, for patients with MF, the survival probability (SP) at 2, 5, and 10 years for HI vs NH were 94%, 87%, and 77% vs. 91%, 81%, and 69%, respectively. The survival difference observed favored HI (p < 0.001). For patients with SS, there was no statistically significant survival difference between HI and NH with 2, 5, and 10 year SP at 65%, 42%, and 17% for HI and 62%, 36%, and 16% for NH, respectively (p = 0.99). In patients with SS, the median survival time in years was 3.3 and 3.2 in NH and HI patients, respectively. In patients with MF, the median survival time was not reached. On multivariate analysis, when adjusted for age, those patients with MF and SS who were older than 80 y.o and between 60 to 80 y.o, had worse OS compared to those younger than 60 y.o, with HR 17.6 (95%: 13.8 – 22.3 ) and 4.2 (95 % CI: 3.6 – 5) respectively for MF; and HR 1.8 (95% CI: 0.9 – 3.7) and 1.64 (CI 95% 1 – 2.8) respectively for SS. Conclusions: We identified ethnic differences in incidence, age at diagnosis, sex, and survival outcomes in patients with MF and SS. Notably, we identified a survival advantage in patients with MF that favored HI. In patients with SS, there was no ethnic difference in survival.