Kaposi sarcoma incidence and survival among HIV-infected homosexual men after HIV seroconversion

Abstract

Background: Despite the success of combination antiretroviral therapy (cART) in reducing the incidence of Kaposi sarcoma, HIV-infected individuals who have responded to treatment continue to be diagnosed with Kaposi sarcoma. We examine factors associated with the incidence of Kaposi sarcoma among cART-treated HIV-infected homosexual men and changes in their survival after its diagnosis over calendar time.

Methods: Data were from HIV-infected homosexual men with well-estimated dates of HIV seroconversion (ie, change in status from being HIV negative to having HIV antibodies detected). Incidence of Kaposi sarcoma was calculated. We used Kaplan-Meier methods to determine survival after Kaposi sarcoma diagnosis in three calendar periods: before 1996, 1996-2000, and 2001-2006. Poisson models were used to examine the effect of risk factors such as current and nadir CD4 cell count (ie, the lowest CD4 cell count ever recorded for a person), duration of infection, and age at diagnosis for Kaposi sarcoma incidence in cART-treated men. All statistical tests were two-sided.

Results: Among the 9473 men, 555 were diagnosed with Kaposi sarcoma in the period 1986-2006, of whom 319 died. The percentage surviving 24 months after Kaposi sarcoma diagnosis rose statistically significantly during the study period from 35% (95% confidence interval [CI] = 29% to 42%) before 1996 to 84% (95% CI = 76% to 90%) in 1996-2000 and to 81% (95% CI = 70% to 88%) in 2001-2006 (P < .001). Seventy men were diagnosed with Kaposi sarcoma after starting cART. Current (ie, within 6 months) CD4 cell count was associated with incidence of Kaposi sarcoma among cART-treated men (rate ratios [RRs] = 18.91, 95% CI = 8.50 to 42.09, for CD4 level category <200 cells per cubic millimeter; RR = 3.55, 95% CI = 1.40 to 9.00, for 200-349 cells per cubic millimeter; and RR = 4.11, 95% CI = 1.74 to 9.70, for 350-499 cells per cubic millimeter; all compared with > or = 500 cells per cubic millimeter). After adjustment for current CD4 cell count, HIV infection duration, age, or nadir CD4 cell count was not associated with Kaposi sarcoma incidence.

Conclusions: Among cART-treated HIV-infected homosexual men, current CD4 cell count was the factor most strongly associated with the incidence of Kaposi sarcoma. Survival estimates after Kaposi sarcoma diagnosis have improved over time.

Figure 1

Crude Kaposi sarcoma (KS) incidence rates according to time since initiation of combination antiretroviral therapy (cART). Confidence intervals (as shown by error bars) were computed by assuming a Poisson distribution for the number of events. cART naive = KS incidence rates in patients who did not start cART; PY = person-years.