Anal cancer rates in HIV patients are "still extremely high," with no apparent protection from antiretroviral therapy, French registry data show.
The anal cancer risk was high even for patients with high CD4 cell counts.
The results, researchers say, suggest that combination antiretroviral therapy (cART), despite strengthening the immune system, does not help control human papillomavirus (HPV) and may in fact be linked to development of HPV-related precancerous cells.
Dr Michael Silverberg, an HIV researcher at Kaiser Permanente Northern California in Oakland who was not involved in the French study, said, "It is not surprising that ART did not have a significant protective effect. In fact, the risk seemed to be higher among ART users, similar to findings of others. This probably reflects the slow oncogenic effects of human papillomavirus."
HIV-positive patients are living longer, but their restored immune function may not be clearing HPV.
"Current thinking is that people with HIV infection have had more frequent HPV infections, and that they have reduced clearance of HPV infections," Dr James Goedert, a senior investigator at the National Cancer Institute's Division of Cancer Epidemiology and Genetics, said. "Longer survival with HIV, thanks to combination antiretroviral therapy, permits the emergence of these relatively long incubation period malignancies."
Dr Goedert too was not involved with the French study, which was headed by Dr Christophe Piketty of the Hopital Europeen Georges Pompidou in Paris.
Implement HPV vaccination
Researchers analysed data on 263 HIV-positive patients with invasive anal cancer drawn from a database of patient information from 69 French teaching hospitals between 1989 and 2008.
They compared these individuals to another 2 012 patients with invasive anal cancer drawn from general-population French cancer registries.
The investigators divided HIV-positive patients by time period of diagnosis: pre-cART (1992-1996) and early (1997-2000), intermediate (2001-2004), and recent (2005-2008) cART eras.
Among HIV-infected patients, the hazard ratio (HR) was 2.5 for developing anal cancer in the cART periods vs the pre-cART period.
Compared to people in the general population, HIV patients also had extremely high anal cancer rates, even in the most recent period studied from 2005-2008, when cART had been in use for the greatest amount of time.
For example, compared with the general population, HIV-infected men who have sex with men had a standard incidence ratio (SIR) of anal cancer of 109.8 for the period of 2005-2008.
Even patients with restored immune function had high rates of invasive anal cancer.
Among patients with a current CD4 cell count of at least 500/uL for at least two years before the diagnosis of anal cancer and whose lowest CD4 count was more than 200/uL, the SIR for anal cancer was 25.
In terms of reducing the risk of anal cancer, Dr Goedert said HPV vaccination should be widely implemented, although that will only help "the next generation with HIV."
For the current population of HIV-positive patients, "The controversy is whether or not to screen for anal pre-cancer with anal cytology," Dr Goedert said. "Clearly, monitoring HIV-infected patients for anal disease needs to be assiduous, with treatment appropriate to whatever anal disease is found."
(Reuters Health, October 2012)
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