HIV infected individuals are 70% more likely to develop lung cancer, even after adjustment for major lung cancer risk factors such as smoking, according to the results of a study published online in the journal AIDS last month.
Several studies had already found increased rates of lung cancer amongst HIV infected individuals however it had been thought much of the increase was the result of higher smoking rates rather than the disease itself. The prevalence of smoking in HIV infected individuals is around 65% in the USA – more than twice the national average.
The study, led by Dr. Keith Sigel of the Mount Sinai School of Medicine, involved 37,294 HIV-positive patients and 75,750 HIV-negative patients from the Veterans Aging Cohort Study (VACS). The researchers found that HIV infection increased the risk of developing HIV by 70%, even after adjustment for other factors such as smoking, COPD, and previous bacterial infection. The incidence rate in HIV negative individuals was 119 per 100,000 per year compared to 204 per 100,000 per year in HIV positive individuals.
The researchers noted that while the risks of lung cancer associated with HIV are quite significant, they still pale in comparison to the impact smoking has on lung cancer. Current smokers have an 8-fold increased risk of lung cancer compared to non-smokers meaning that a non-smoking HIV-positive individual is still less than a quarter as likely to develop lung cancer as a smoker who is HIV-negative.
In the past, it had been thought that the increased cancer risk in HIV infected individuals was limited to Kaposi’s sarcoma, non-Hodgkin’s lymphoma, and cervical cancer, the so-called “AIDS-defining cancers”. Recent research however has linked HIV status to a variety of other cancers including Hodgkin’s lymphoma, liver, lung, anal, head, and neck cancer. Since the advent of anti-retroviral therapies the incidence of AIDS-defining cancers has dropped significantly however the incidence of non-AIDS defining cancers has actually increased.
A 2009 study, published in the Journal of Acquired Immune Deficiency Syndromes found that the overall risk of non-AIDS-defining cancers was 60% higher in HIV positive individuals compared to HIV negative individuals. The forms of cancer most strongly related to HIV-positive status were anal cancer (IRR=14.9), Hodgkin’s lymphoma (IRR=4.6), liver cancer (IRR=2.8), lung cancer (IRR=2.0), and melanoma (IRR=1.7).
The researchers also found that those with a low CD4 count (reflecting poorly controlled HIV), were more likely to develop Hodgkin’s lymphoma and anal cancer.
The increased risk of developing non-AIDS-defining cancers is thought to be due to either mild immunosupression, or the persistence of low level inflammation that occurs even when HIV is well controlled with anti-retroviral therapies. HIV sufferers also have a higher prevalence of Epstein–Barr virus (EBV) which is linked to Hodgkin’s lymphoma, Human papillomavirus (HPV) which increases the risk of cervical and anal cancers, and Hepatitis B & C infection – a major cause of liver cancer.
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