Kaposi sarcoma trends in Uganda and Zimbabwe: a sustained decline in incidence?

Trends in Kaposi sarcoma (KS) incidence over four decades were described for Zimbabwe and Uganda. KS data were retrieved from the population-based cancer registries of Bulawayo (1963-1971) and Harare (1990-2005), Zimbabwe and Kyadondo, Uganda (1960-1971 and 1991-2007). Joinpoint regression models were used to analyze time trends of KS incidence. Trends were compared to HIV/AIDS trends and were also described as rates versus birth cohort by age. In both countries, an increased incidence of KS accompanied the emergence of the HIV/AIDS epidemic (p-value < 0.0001). In Zimbabwe, KS incidence (both sexes, all ages) changed in parallel to that of HIV/AIDS prevalence, whereas in Uganda, despite an observed decrease in HIV/AIDS prevalence since 1992, we observed a decrease in KS incidence in men younger than 50 years (Annual Percent Change, APC after 1991 = -4.5 [-5.6; -3.4], p-value < 0.05) but not in men aged >50 years (APC after 1991 = 1.0 [-2.8; 5.0]) nor in women (APC = 1.0 [-0.6; 2.6]). In both populations, a period effect at older ages was observed, with initial increases in incidence in men followed subsequently by a downturn in rates of the same magnitude. The uniformly declining rates in younger men (aged less than 30 years) suggested that a recent cohort effect was also in operation with a reduced risk in generations born after the mid-1950s in Uganda and in the mid-1960s in Zimbabwe. The combined introduction of antiretroviral therapy and effective prevention programmes against HIV/AIDS appeared to be the key contributors to the KS decline observed in both Uganda and Zimbabwe.