Changes in Cancer Risk Found for Human Immunodeficiency Virus
The Bottom Line
Since the widespread introduction of highly active antiretroviral therapy (HAART) to treat HIV infection, the incidence of Kaposi sarcoma (KS) and non-Hodgkin lymphoma (NHL) among HIV-infected individuals in the United States has decreased and the incidence of certain non-AIDS-related cancers has increased.
The Whole Story
HIV-infected individuals have an increased risk of cancer, which, in the past, has mostly been explained by significantly higher rates of KS and NHL among these people. The increased incidence of these two cancer types was thought to be a consequence of the immune system's reduced ability in HIV-infected individuals to fight infections by cancer-causing viruses (specifically, human herpesvirus 8 for KS and Epstein-Barr virus for NHL).
With the introduction of highly active antiretroviral therapy (HAART), which became widely available in 1996, individuals infected with HIV are living substantially longer due to the partial restoration of their immune system's function. Therefore, researchers wanted to know whether HAART has led to reductions in cancer risk and what the current pattern of cancer is among HIV-infected individuals.
To analyze the spectrum of cancers among HIV-infected individuals, data from HIV/AIDS and cancer registries in Florida, Colorado, and New Jersey were pooled to create a study group of 57,350 HIV-positive individuals who had not yet developed AIDS. Researchers then examined the patterns of cancer incidence in two time periods: 1991-1995 (the pre-HAART era) and 1996-2002 (the HAART era).
Overall, cancer incidence declined by about 10 percent in the HAART era compared to the pre-HAART era. This decline was due mainly to large reductions in the incidence of KS and certain types of NHL; however, even in the HAART era, the incidence of these cancers remains much higher among HIV-infected individuals than among uninfected persons.
The declines in KS and NHL in the HAART era support the idea that HAART-related improvements in immune system functioning can help lower the risk of certain cancers among HIV-infected individuals. The importance of the immune system in preventing these cancers is also highlighted by their increased incidence following a diagnosis of AIDS and with decreasing blood levels of CD4-positive T lymphocytes.
In the pre-HAART era, non-AIDS-related cancers represented approximately 34 percent of all cancers among HIV-infected individuals; in the HAART era, this percentage increased to 58 percent. This change reflects both the declines in incidence of KS and NHL and the increased incidence of certain non-AIDS-related cancers, including Hodgkin lymphoma and cancers of the anus, larynx, liver, and pancreas, in the HAART era compared to the pre-HAART era.
These findings demonstrate the need for continued monitoring of HIV-infected individuals. Such monitoring may reveal additional changes in cancer risk over time and prompt the development of new strategies for screening and early intervention.
More summaries of selected scientific advances from NCI-supported research are available at http://www.cancer.gov/aboutnci/servingpeople/advances.