People with HIV Are at Higher Risk for Cancers Linked to Smoking, Viruses

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People with HIV appeared to have a higher overall rate of cancer in a large Danish study, but the difference was only significant for malignancies caused by smoking or other viruses, including lung cancer, anal cancer, and liver cancer. A related U.S. study found the rate of prostate cancer was actually lower among HIV positive men.

Since the advent of effective combination antiretroviral therapy (ART) in the mid-1990s, rates of AIDS-defining cancer -- Kaposi sarcoma, non-Hodgkin lymphoma, and cervical cancer -- have fallen. Although results have been mixed, most studies have found that people with HIV remain at higher risk for certain malignancies compared to HIV negative populations. Thanks to effective HIV treatment, in fact, more people with HIV are staying alive long enough to develop cancer.

Smoking and Viral Cancers

As described in the June 19 edition of AIDS, Marie Helleberg from Copenhagen University Hospital and colleagues looked at rates of different cancers among HIV positive and negative people and estimated "population-attributable fractions" (PAFs), or the proportion of cancers associated with having HIV, immune deficiency (as indicated by CD4 T-cell count), and smoking. They specifically looked at cancers related to smoking (like lung and mouth cancer) and those caused by viruses including human papillomavirus (HPV; anal and cervical cancer), hepatitis B or C (liver cancer), and Epstein-Barr (some types of lymphoma).

This nationwide population-based cohort study compared cancer incidence (new cases) between 3503 people with HIV and 12 ,979 matched HIV negative population controls. Among people with HIV, the average baseline CD4 count was 450 cells/mm3 -- indicating relative well-preserved immune function -- and most were on antiretroviral therapy.

Results

o   Virus-related cancers: IRR 11.5, or more than 11-fold higher risk;

o   Smoking-related cancers: IRR 2.8, or nearly 3 times higher risk.

"The risk of cancer is increased in HIV patients compared to the background population," according to the study authors. "In absence of smoking, the increase in risk is confined to cancers related to viral infections, whereas the risk of other cancers is not elevated and does not seem to be associated with immune deficiency."

Prostate Cancer

A second study, published in the May 12 advance edition of Journal of Acquired Immune Deficiency Syndromes, looked at prostate cancer risk among men with HIV. This cancer is not known to have a viral cause and its association with smoking is unclear.

Julia Marcus from Kaiser Permanente Northern California and colleagues aimed to determine whether previously reported lower prostate cancer incidence rates among HIV positive men is attributable to confounding factors, reduced screening, or some other reasons.

This cohort study included 17,424 HIV positive and 182,799 HIV negative participants in Kaiser Permanente's managed health organization in Northern and Southern California. Fewer than half were on ART at study entry, rising to 76% by the end, but the mean CD4 count was relatively high at 466 cells/mm3. HIV positive men were more likely than negative men to smoke (39% vs 23%) and to have testosterone deficiency (13% vs 1%).

Participants were followed from their first Kaiser Permanente enrollment (after January 1996 in Northern California and after January 2000 in Southern California) until prostate cancer diagnosis, loss to follow-up, or December 2007. The mean duration of follow-up was nearly 5 years.

The researchers compared cancer rates by HIV status, adjusting for age, race, smoking, alcohol or drug use, being overweight or obese, and diabetes. For the Northern subset, they also looked at testosterone deficiency and prostate-specific antigen (PSA) tests as a proxy for cancer screening.

Results

"Prostate cancer incidence rates are lower in HIV positive compared with HIV negative men, which is not explained by screening differences or the risk factors evaluated," the researchers concluded.

Taken together, the findings from these 2 studies indicate that people with HIV are at higher risk of some -- but by no means all -- cancers. Preventive measures can help reduce the likelihood of some of these disproportionate cancers, including regular screening, smoking cessation, and receiving hepatitis B and possibly HPV vaccines.

6/11/14

References

M Helleberg, J Gerstoft, S Afzal, et al. Risk of cancer among HIV-infected individuals compared to the background population: impact of smoking and HIV. AIDS 28(10):1499-1508. June 19, 2014.

JL Marcus, CR Chao, WA Leyden, et al. Prostate cancer incidence and prostate-specific antigen testing among HIV-positive and HIV-negative men.Journal of Acquired Immune Deficiency Syndromes. May 12, 2014 (Epub).