RISK FACTORS FOR AIDS ASSOCIATED NON-HODGKIN'S LYMPHOMA: A CASE-CONTROL STUDY.

Abstract

S6 Background: Although non-Hodgkin's lymphoma (NHL) occurs in more than 5% of people with AIDS, little is known of risk factors for this malignancy. The one clear risk factor is severity of immune deficiency. Our study was designed to identify other risk factors for NHL, including demographic, clinical and laboratory factors. Methods: 219 people with AIDS-NHL diagnosed in Sydney prior to 1995 were compared to 219 HIV positive controls matched for degree of immune deficiency as indicated by CD4 lymphocyte count. Data on risk factors were abstracted by medical record review. Results: AIDS and cancer register linkage confirmed that all registered cases of AIDS-NHL in the study area were included. The CD4 counts of cases and controls did not differ significantly (p = 0.66). NHL risk was associated with indices of prolonged immune deficiency including longer time since seroconversion (median of 6.5 and 5.0 years in cases and controls for whom this was known, p = 0.001), lower CD4 count one year prior to diagnosis (p trend 0.003) and a prior diagnosis of mycobacterium avium complex disease (OR 3.2, 95% CI 1.2-10). Markers of immune stimulation, including raised serum globulin (p trend 0.015), IgG (p trend 0.026), and HIV p24 antigen positivity (OR 2.0, 95% CI 1.3-3.3) were also associated with risk of NHL. Indices of lytic EBV infection, including a prior diagnosis of oral hairy leukoplakia and receipt of anti-herpesvirus therapy, were not associated with risk, although receipt of ganciclovir prior to diagnosis was non-significantly protective (OR 0.51, 95% CI 0.20-1.25). Total dose of AZT received was not related to risk of NHL, and the highest dose level of ddC was associated with a decreased risk of NHL (OR 0.38, 95% CI 0.17-0.82). Conclusion: These data indicate that prolonged immune deficiency and immune stimulation are risk factors for NHL in people with HIV. This study does not support a role of anti-EBV therapy in NHL prophylaxis. Our results suggest that effective anti-HIV therapy may decrease the risk of NHL by decreasing immune stimulation.