Adult T‐cell leukemia/lymphoma in French Guiana (1990–2019): Epidemiology, clinical features, and <scp>HTLV</scp> ‐1 genetic diversity in the two main ethnic populations

Adult T-cell leukemia/lymphoma (ATL) is a rare and aggressive malignancy caused by human T-cell leukemia virus type 1 (HTLV-1). French Guiana, located in northeastern South America, is a region of high HTLV-1 endemicity with a multiethnic population. We conducted a comprehensive 30-year study of ATL cases diagnosed between 1990 and 2019, capturing nearly all confirmed ATL cases in the territory (n = 137). The predominant subtypes were lymphoma (58%) and acute ATL (36%). Striking ethnic disparities emerged: 69% of patients were Maroons, and the median age at diagnosis was 43 years among Maroons versus 58 years among Creoles. Survival outcomes were uniformly poor, with median overall survival of 2.7 months for acute and 5.2 months for lymphoma ATL. In multivariate analysis, acute ATL subtype and hepatosplenomegaly at diagnosis were independently associated with worse survival. Complete HTLV-1 genome sequences were obtained for seven ATL cases, and phylogenetic analysis of complete genomes revealed strong ethnic clustering: all Creole strains belonged to the Transcontinental subtype, while all Maroon strains belonged to the West African subtype. Moreover, HTLV-1 seroprevalence in the general population was measured among 1078 Creoles tested in 1998, with a prevalence of 3.1%, markedly lower and occurring at older ages compared to previously published data for the Maroon population. Our findings highlight pronounced disparities in ATL epidemiology by ethnic group and emphasize the need for targeted prevention, early diagnosis, and improved care in high-risk populations.