AIDS-related cancers in the era of highly active antiretroviral therapy.

Highly active antiretroviral therapy (HAART) has shown great efficacy in reducing human immunodeficiency virus levels, increasing immunity, and prolonging the survival of persons with acquired immunodeficiency syndrome (AIDS). The risk of life-threatening infections has been greatly reduced. However, the impact of HAART on the incidence of malignancy has been less clear. Published studies generally show that the risk of developing Kaposi's sarcoma declined by about two-thirds between 1994 and 1995 and from 1996 onward (considered the HAART era). Even before 1994, the risk for Kaposi's sarcoma in persons with AIDS had declined considerably and this cancer has now become relatively uncommon. The mechanism by which this decline in incidence was achieved appears to involve improved immunity. Data on the reduction in the risk for non-Hodgkin's lymphoma are mixed. Several studies conducted between 1997 and 1999 found no reduction in the risk for non-Hodgkin's lymphoma, although the most recent data (from 1997 to 1999) show a 42% decrease in risk. Even with a one-third reduction, the risk for non-Hodgkin's lymphoma remains considerably elevated. This high risk may be related to the fact that HAART therapy does not restore the immune system to normalcy. The increased lymphocyte turnover, with its accompanying risk of genetic errors, may increase the risk of developing non-Hodgkin's lymphoma. Most reports have insufficient data to analyze the impact of HAART therapy on incidence of central nervous system lymphomas, but recent data (from 1997 to 1999) showed a significant reduction in that risk. The mechanism by which this might occur is unclear because the central nervous system is an immunologic sanctuary. The relatively low incidence of other cancers in persons with AIDS makes it difficult to gauge the effect of HAART on their incidence, but to date, no significant trends have been reported for specific tumor types or for the overall risk of non-AIDS-related cancers.