Kaposi's sarcoma and central nervous system disease: A real association or an artifact of the control group?

Objectives: To test the hypothesis that Kaposi's sarcoma (KS) protects against four central nervous system (CNS) diseases in HIV-1-infected individuals. Study population and design: The study population of 9404 subjects included participants in Terry Beirn Community Programs for Clinical Research on AIDS (CPCRA) protocols who were enrolled between September 1990 and September 1998. This was an observational study. Methods: Proportional hazards regression was used to estimate adjusted relative risks for predictors of four central nervous system diseases. Covariates included occurrence of Kaposi's sarcoma, occurrence of other opportunistic infections or malignancies, baseline CD4+ count, and other baseline characteristics. Results: Among the 5944 participants without progression to AIDS at entry, 451 developed a CNS disease. The adjusted relative risk of any CNS disease for those who developed Kaposi's sarcoma versus those who did not develop any AIDS-defining event was 1.41 [95% confidence interval (CI), 0.98-2.03; P = 0.06]. In contrast, the adjusted relative risk of any CNS disease for those with Kaposi's sarcoma versus those with some other non-Kaposi's sarcoma AIDS-defining event was 0.37 (95% CI, 0.24-0.57; P < 0.0001). Among the 3460 participants with progression to AIDS at entry, the adjusted relative risk of any CNS disease for those with Kaposi's sarcoma versus those with some other non-Kaposi's sarcoma AIDS-defining event was 0.71 (95% CI, 0.40-1.25; P = 0.23). Conclusions: Our analyses indicate that the risk of CNS disease associated with Kaposi's sarcoma depends strongly on the reference or control group chosen. When compared to individuals with other non-Kaposi's sarcoma AIDS-defining diseases, Kaposi's sarcoma is associated with a lower risk of CNS disease in HIV-1 positive individuals. However, when compared to individuals with no AIDS-defining disease or with a similarly mild AIDS-defining disease such as invasive candidiasis, Kaposi's sarcoma is associated with an equivalent risk of CNS disease. (C) 2000 Lippincott Williams and Wilkins.