Advanced clinical characteristics and survival disparities of patients with primary cutaneous T-cell lymphoma in nonmetropolitan regions in the United States

Summary: Abstract Body: The incidence of cutaneous T-cell lymphoma (CTCL) in the United States (US) has been increasing in metropolitan areas, but it remains unclear how survival outcomes in these areas compare to those in nonmetropolitan regions. This retrospective cohort study sought to compare the clinical presentations and disease-specific survival of patients with CTCL residing in metropolitan versus nonmetropolitan regions using SEER data. We identified 12,320 metropolitan and 1,073 nonmetropolitan patients with histologically confirmed primary CTCL diagnosed between 2000 and 2021. Kaplan-Meier survival curves and cumulative incidence functions were utilized to evaluate overall survival and disease-specific mortality. Cox proportional hazard models and Fine-Gray competing risk regression models were used to compare overall mortality and disease-specific mortality. Nonmetropolitan patients were older (63 vs. 57 years) and more likely to present with visceral disease (10.0% vs. 8.5%) than metropolitan patients. Nonmetropolitan patients demonstrated significantly lower 5-year overall survival rates (72.1% vs. 81.5%) and higher 5-year disease-specific mortality rates (15.1% vs. 10.3%) compared to metropolitan patients. These findings remained consistent in both multivariable Cox proportional hazard models and Fine-Gray competing risk regression models. Our study highlights that patients in nonmetropolitan regions were more likely to be diagnosed at an older age and with more advanced disease, with correspondingly worse disease-specific survival compared to patients in metropolitan areas. The reason for this disparity is likely multifactorial, but could result from reduced healthcare access, lower dermatologist density, or environmental exposures. Further research is needed to understand and address these regional survival differences. Daniel Y. Kim^{1, 2, 3}, MM Shinohara⁴, Sasha Stephen^{1, 2, 3}, Thomas S. Kupper^{1, 2, 3}, Cecilia Larocca^{1, 2, 3}, Nicole R. LeBoeuf^{1, 2, 3} 1. Harvard Medical School, Boston, MA, United States. 2. Dermatology, Brigham and Women's Hospital, Boston, MA, United States. 3. Dermatology, Dana-Farber Cancer Institute, Boston, MA, United States. 4. Dermatology, University of Washington, Seattle, WA, United States. Clinical Research: Epidemiology and Observational Research