Risk of cancers with infectious cause going down in people with HIV

A large study of HIV-positive people in the US, followed for an average of four years, shows that people with HIV have an approximately sixfold greater risk of developing a non-AIDS-defining cancer with an infectious cause compared to HIV-negative people, with the majority of these cancers potentially related to human papilloma virus (HPV). The findings, from the Kaiser Permanente healthcare database in California, were presented on Monday at the Sixteenth Conference on Retroviruses and Opportunistic Infections in Montreal, Canada.

Nevertheless the study found that for people with HIV, the risk of developing a non-AIDS-defining cancer with an infectious cause has declined since the introduction of antiretroviral therapy, whereas it has remained constant in HIV-uninfected people since 1996.

Non-AIDS-defining cancers are becoming more common as the population of people with HIV lives longer and ages. Some non-AIDS-defining cancers, such as lung cancer, occur more frequently in people with HIV than in the general population, and a recent US study showed that nine non-AIDS-defining cancers occurred more frequently in people with HIV than in the general US population.

However, it is not clear if the risk of developing such cancers is increasing, or diminishing due to the effects of antiretroviral therapy.

The analysis reported today looked at the incidence of cancers in HIV-positive people receiving care through the Kaiser Permanente managed healthcare programme, which provides care for around one in four Californians. The researchers identified 18,890 HIV-positive patients and 189,804 HIV-negative patients.

Information on cancers was collected from the Kaiser Permanente’s cancer registry, and cancers were grouped as infection-related or unrelated. Infection-related cancers were considered to be those of the head, neck, liver, anus, and cervix, as well as Hodgkin’s lymphoma. (However, it should be noted that the vast majority of head and neck cancers are caused by smoking or alcohol consumption; Epstein-Barr virus and human papilloma virus are thought to have a less significant role in the development of these cancers).

There were 480 non-AIDS-defining cancers in HIV-positive people: 220 were infection-related and 269 non-infection-related. In HIV-negative people there were 3065 non-AIDS-defining cancers: 398 infection-related and 2698 non-infection-related.

The relative risk of the two types of cancers between HIV-positive and HIV-negative people was as follows:

• Infection-related: 29.7 per 10,000 person-years in people with HIV, 4.4 per 10,000 person-years in HIV-uninfected people (relative risk 6.8, p
• Infection-unrelated: 36.4 in people with HIV vs 30.6 in people without (relative risk 1.2, p = 0.002). When the relative risk was compared over three time periods (1996-1999, 2000-2003, 2004-2006) the difference was only significant in the 2004-2006 period (RR1.3, p = 0.002).

The most pronounced differences for infection-related cancers occurred in:

• Anal cancer (80-fold higher risk in HIV-positive people)
• Hodgkin’s lymphoma (19-fold higher risk)
• Liver cancer (2.7-fold higher risk)

There was no significant change in the risk of Hodgkin’s lymphoma, liver cancer or oropharyngeal cancers over time, but there was a 6% annual decline in the risk of anal cancer (P

For infection-unrelated cancers, HIV-positive people were found to have a higher risk of:

• Kidney
• Lung
• Melanoma
• Prostate cancer

There was also a suggestion of an increased risk of colorectal cancer in recent years, Dr Silverberg said.

He noted that the findings have limited generalisability to women and the uninsured, due to the fact that while the cohort reflects the epidemiology of HIV in California quite closely, 74% of identified cases were in men who have sex with men.