EFFECT OF HUMAN T-LYMPHOTROPIC VIRUS TYPE-I INFECTION ON NON-HODGKINS-LYMPHOMA INCIDENCE

Background: We previously reported from a case-control analysis that T -cell non-Hodgkin's lymphoma (NHL) was strongly associated with human T-lymphotropic virus type I(HTLV-I) infection in Jamaica and Trinidad and that the relative risk for HTLV-I infection was very high in young er patients, Purpose: The objective of this study was to estimate the age-specific incidence rates of NHL among HTLV-I-infected and HTLV-I-u ninfected adults in Jamaica and Trinidad, Methods: Population rates of HTLV-I infection were calculated from available census reports and se rosurvey data, Incidence rates for NHL were calculated from all incide nt cases in Jamaica during 1984-1987 (n = 135) and from all incident c ases in Trinidad during 1986-1990 (n 117), Using biopsy material, we d etermined whether the immunophenotype of the tumor cells was T cell, B cell, or other, NHL incidence rates were computed according to HTLV-I status, age, sex, and tumor phenotype for each country separately and for both countries combined by weighting to the relative population s ize of each country, Results: The age-standardized NHL incidence rate (mean +/- SE) in Jamaica was 1.9 +/- 0.2 per 100000 person-years (PY), In Trinidad, the rate was 2.9 +/- 0.4 per 100000 PY. Overall, the inc idence of NHL increased with age and was higher in males than in femal es, In the HTLV-I-infected population, the incidence of NHL was invers ely related to age, and age specific rates were higher in males than i n females, The NHL incidence in those estimated to have acquired HTLV- I infection in childhood, however, showed no sex difference, and one i n 1300 such carriers (95% confidence interval: one in 1100 to one in 1 600) per annum were estimated to be at such risk, For T-cell NHL, as p roxy for adult T-cell lymphoma/leukemia, incidence was highest in thos e patients infected with HTLV-I early in life (perinatally or via brea st milk), with high, sustained risk from early adulthood in both sexes , Conclusions: While overall NHL incidence rates reveal that HTLV-I en demicity does not impose an exaggerated lymphoma burden on these popul ations, the risk for lymphoma among carriers who acquire infection ear ly in life is dramatic and is consistent with the hypothesis that viru s exposure early in life is most important for lymphomagenesis, Implic ations: Studies of HTLVI carriers known to be infected in childhood ma y provide insight into markers intermediate in the lymphoma-genetic pr ocess, Strategies to disrupt early-life transmission of HTLV-I, notabl y mother-infant transmission, may be critical in reducing the burden o f lymphoreticular disease in these populations