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Starting HAART With High CD4 Counts Reduces Incidence of Squamous Cell Anal Cancer: Presented at CROI

By Ed Susman

SAN FRANCISCO -- February 22, 2010 -- Patients with HIV who begin antiretroviral therapy before their CD4-positive cell counts drop below 200 cells/mm³ appear to have significantly reduced risk of developing squamous cell cancer of the anus, researchers said here at the 17th Conference on Retroviruses and Opportunistic Infections (CROI).

"Although the crude incidence of squamous cell cancer of the anus in HIV-infected individuals is higher among those who ever received highly active antiretroviral therapy [HAART], the risk of squamous cell cancer of the anus is significantly lower in patients with re-therapy nadir CD4 counts of 200 or less, and the risk decreases with higher adherence to therapy," said Elizabeth Chiao, MD, Baylor College of Medicine, Houston, Texas.

"Initiating highly active antiretroviral therapy at higher CD4 counts and optimising adherence may decrease the risk of subsequent squamous cell cancer of the anus," she said during her poster presentation on February 19.

Dr. Chiao and colleagues performed a retrospective cohort study utilising data from the Veterans Affairs Immunologic Case Registry from 1987 to 2007, which contains laboratory and pharmacy data, as well as ICD-9 diagnosis codes of all HIV-positive veterans.

"We identified 36,788 individuals in the cohort," she said. "Of these, 20,085 received at least 1 prescription for highly active antiretroviral therapy medications."

When researchers compared outcomes among those who received antiretroviral treatment with the total cohort, the incidence rate of anal cancer was significantly higher in those who received HAART and those who did not. The rate was 1.25/1,000 person-years among those not on HAART and was 1.91/1,000 person-years among those who received therapy (P < .05).

When the researchers drilled down into the data, they noted that patients who started therapy when CD4-positive cell counts were <200 cell/mm³ and had <40% adherence rate to prescribed medication had significantly higher risks of developing anal cancer when compared with patients who began treatment at higher CD4 count and maintained an 81% to 100% adherence rate (P = .003).

For the purpose of the study, HAART was defined as a regimen that included 2 nucleoside reverse transcriptase inhibitors drug classes and 1 drug from either the non-nucleoside reverse transcriptase class or the protease inhibitor class. Adherence was calculated on cumulative percent time on therapy.

More than 98% of the patients in the study were men and more than 90% were aged about 30 years.

[Presentation title: The Effect of HAART on the Incidence of Squamous Cell Cancer of the Anus. Abstract 767]

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