Wednesday, September 30, 2009

Immune suppression has important role in development of non-AIDS cancers

Immune suppression plays an important part in the development of non-AIDS-defining cancers in people with HIV, Australian investigators argue in a letter published in the June 1st edition of AIDS. The investigators were prompted to write to the journal after the publication of a US study earlier this year that found that neither CD4 cell count nor use of antiretroviral therapy were risk factors for such cancers. The authors note that this study, which involved 4500 individuals diagnosed with HIV between 1984 and 2006, did not include an analysis of the impact of the cumulative duration of immune suppression on cancer risk. Furthermore, they refer to the findings of other research that shows a clear link between the risk of non-AIDS-defining cancers and immune suppression. The D:A:D study examined risk factors for death due to cancer in 23,500 patients taking antiretroviral therapy. Among the risk factors for death from a non-AIDS-defining cancer were latest CD4 cell count. Univariate analysis of the results of this study also showed that the cumulative duration of immune suppression, defined as time spent with a CD4 cell count below 200 cells/mm3 was also significant. Research conducted by investigators at the Chelsea and Westminster Hospital in London also showed that a lowest ever CD4 cell count below 200 cells/mm3 and use of antiretroviral therapy were risk factors for the development of a non-AIDS-defining cancer. This research involved over 11,000 patients who attended the hospital between 1983 and 2007. “We believe that the findings from these studies suggest that HIV-related immunosuppression does play an important role in the risk of specific cancers in the HAART era”, comment the authors. They also note “the remarkable similarity in the range of cancers occurring at excess rates in solid organ transplant recipients and people with HIV infection strongly supports an effect of long-term immunosuppression on cancer incidence.” Accordingly, the authors recommend that future large cohort studies should examine “the independent effects of ageing, the time-dependent severity of immunosuppression, and the cumulative duration of immunosuppression on cancer risk.” They also recommend that the role of these factors in the development of individual cancers, or groups of cancers, such as those caused by the same virus, should be examined. They believe that such analyses “will assist in the development of strategies to minimize or prevent the occurrence of cancer in patients with long-term immune deficiency.”


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