Further evidence that HIV-positive men have higher rates of anal cancer

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HIV-positive men are at significantly greater risk of developing anal cancer than men who do not have HIV, say US researchers writing in the Journal of Acquired Immune Deficiency Syndromes. As HIV therapy means HIV-positive people are living longer, they add, this cancer is posing an increasing problem.

The incidence of anal cancer has increased in the past decade – particularly among some subgroups of the population. It is already known that HIV-positive men - and men who have sex with men - are at increased risk of anal cancer compared to the general population. Now researchers at the John Hopkins Bloomberg School of Public Health in Baltimore have compared the incidence and risk factors for anal cancer in HIV-positive and HIV-negative men who have sex with men.

In the follow-up period between 1984 and 2006 there were 28 cases of anal cancer in the 6972 men studied. But the incidence was almost five times greater in HIV-positive men - with a rate of 69 cases per 100,000 patient years compared to just 14 cases per 100,000 in the HIV-negative group.

Glossary

human papilloma virus (HPV)

Some strains of this virus cause warts, including genital and anal warts. Other strains are responsible for cervical cancer, anal cancer and some cancers of the penis, vagina, vulva, urethra, tongue and tonsils.

cervix

The cervix is the neck of the womb, at the top of the vagina. This tight ‘collar’ of tissue closes off the womb except during childbirth. Cancerous changes are most likely in the transformation zone where the vaginal epithelium (lining) and the lining of the womb meet.

lesions

Small scrapes, sores or tears in tissue. Lesions in the vagina or rectum can be cellular entry points for HIV.

person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.

AIDS defining condition

Any HIV-related illness included in the list of diagnostic criteria for AIDS, which in the presence of HIV infection result in an AIDS diagnosis. They include opportunistic infections and cancers that are life-threatening in a person with HIV.

The researchers also compared incidence rates in the years since effective antiretroviral treatment became available to the pre-treatment era. They found that - among HIV-positive men - the incidence of anal cancer was higher since effective HIV treatment became available – 137 cases per 100,000 person years compared to 30.

It is thought this might be because improved survival is allowing enough time for pre-cancerous lesions to develop into full-blown cases of anal cancer. A further analysis of the data confirmed a previously noted result that the risk of anal cancer rose with increasing number of unprotected receptive anal sex partners among the HIV-positive men.

Anal cancer – like cervical cancer – is associated with infection with the human papillomavirus (HPV). HIV treatment has reduced the risk of many HIV-associated illnesses, but studies like this suggest it does not reduce the risk of HPV-associated anal, genital and oropharyngeal cancers. Although cervical cancer is currently considered to be an AIDS-defining illness, anal cancer is not.

The researchers conclude by saying that anal cancer may be preventable but the benefits of screening for it and treating it have not yet been fully evaluated. They call for further research to calculate the benefits and costs of risk reduction interventions, screening and treating pre-cancerous anal lesions in high-risk individuals such as those living with HIV.

References

D’Souza D et al. Incidence and epidemiology of anal cancer in the multicenter AIDS cohort study. Journal of Acquired Immune Deficiency Syndromes 48, 491-499, 2008.