No comparisons of Kaposi sarcoma (KS) risk are available between regions with different HIV and Human Herpesvirus 8 (HHV-8) prevalence. We examined KS risk in adults on combination antiretroviral therapy (ART) in the IeDEA and COHERE in EuroCoord cohort collaborations.
We included HIV-positive adults (≥ 16 years) who started ART from 1996 onwards. We compared the risk of incident KS between regions using flexible parametric survival models with region-specific baseline hazards, adjusted for age, sex and its interaction with region, time-updated CD4 counts and year of ART start. We excluded Asia-Pacific and Australia from multivariable analyses due to the small sample size. We present hazard ratios (HR) and 95% confidence intervals (CI) by time on ART and at 2 years after ART start.
We included 352,013 patients from Asia-Pacific, Australia, Latin and North America, Southern Africa, and Europe. Median age at ART start was 36 years and similar across regions. Median CD4 count at ART start was <200 cells/µL in Asia, Southern Africa and Latin America, and >200 cells/µL in Australia, Europe and North America. The proportion of men and the subset who have sex with men (MSM) was highest in Australia, followed by North and Latin America and Europe. Over 1.3 million person-years (pys) 2,935 adults developed KS for an overall incidence rate of 199/100,000 pys (95%CI 192-207). After 2 years on ART KS incidence was higher in women from Southern Africa than in European women (adjusted HR 2.5, 95%CI 2.0-3.1), and similar to European women in women from Latin and North America. In men crude KS risk was higher in North America compared to Europe (HR 1.5, 95%CI 1.3-1.9), in multivariable analyses this risk declined to HR 1.1 (95%CI 0.9-1.4). The change was mainly explained by adjusting for time-updated CD4 counts. KS risk was similar in men from other regions (Figure).
Women in Southern Africa had a higher KS risk than women in Europe which was not explained by HIV-related risk factors. In men KS risk was similar across regions after adjusting for HIV-related risk factors. This pattern likely reflects different HHV-8 risk profiles: while men were at high risk of HHV-8 infection in most regions (MSM or resident in HHV-8 endemic regions) the main risk factor for HHV-8 infection in women was residence in endemic regions. Migration data were not available for all regions and hence not considered in the analysis.