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HIV may explain increase in anal cancer incidence among men
HIV infections greatly influenced the recent increase in anal cancer incidence among men in the United States, according to study results.
Anal cancer is rare in the United States, with an estimated 6,230 people — 3,980 women and 2,250 men — expected to be diagnosed this year, according to background information included in the study. However, incidence rates have increased steadily since 1940.
HIV infection is a significant risk factor for anal cancer, the fourth most common cancer found in HIV-infected individuals. However, the degree to which anal cancer incidence in the general population has been influenced by anal cancer cases among HIV-infected individuals is unclear, researchers said.
Meredith S. Shiels, PhD, MHS, of the infections and immunoepidemiology branch of NCI’s division of cancer epidemiology and genetics, and colleagues used data from the HIV/AIDS Cancer Match Study to investigate the impact of HIV on anal cancer incidence.
The researchers focused on data from 17 states and metropolitan areas between 1980 and 2005.
Shiels and colleagues identified an estimated 20,533 anal cancer cases, of which an estimated 1,665 cases (8.1%) involved individuals who were infected with HIV.
The percentage of men with anal cancer who also were HIV-positive increased steadily during the study period, from 1.1% in 1980-1984 to 28.4% in 2001-2005 (95% CI, 26.6-29.4).
In contrast, the percentage of women with anal cancer who also were HIV-positive increased from 0% in 1980-1984 to 1.2% in 2001-2005 (95% CI, 0.93-1.4%).
HIV infection had a strong impact on trends in anal cancer incidence in males, the researchers said.
Among men, annual anal cancer incidence during the entire study period increased by 3.4% (95% CI, 2.9-3.9) overall and by 1.7% (95% CI, 1.2-2.3) among those who were not infected with HIV. Younger age and black race were associated with higher proportions of anal cancer cases with HIV infection, according to researchers.
Among women, annual anal cancer incidence during the entire study period increased by 3.3% (95% CI, 3.0-3.7) overall and by 3.3% (95% CI, 2.9-3.6) among those who were not infected with HIV.
“A large proportion of US males with anal cancer in recent years, particularly young and black males, were HIV-infected,” Shiels and colleagues concluded. “Measures that would effectively prevent anal cancer in HIV-infected males could markedly reduce anal cancer rates at the population level.”
HPV vaccination and anal Pap testing are among the prevention strategies suggested for reducing the burden of anal cancer.
“In contrast, very few females with anal cancer were HIV-infected,” Shiels and colleagues wrote. “More research is needed to understand causes of rising anal cancer incidence in females.”