Gay men are not the
only group of HIV-positive patients who have an increased risk of anal cancer,
according to North American research published in the online edition of Clinical Infectious Diseases. The
researchers found that incidence of the cancer was also significantly higher in
non-gay HIV-positive men as well as HIV-positive women when compared to
individuals in the general population.
“We confirmed that
HIV-infected MSM [men who have sex with men] experienced the greatest risk of
anal cancer,” write the authors. “We also found that both HIV-infected other
men and women had substantially higher rates than HIV-uninfected men and women,
and that HIV-infected other men and women had similar rates.” They believe that
their findings may have implications for anal cancer screening strategies.
Thanks to improvements
in HIV treatment and care the prognosis of many HIV-positive patients is now
near normal. However, HIV-positive patients appear more likely to develop
certain malignancies, including anal cancer, compared to their HIV-negative
incidence of anal cancer in the different populations affected by HIV can help
develop strategies to prevent the cancer.
investigators from the North American AIDS Cohort Collaboration on Research and
Design (NA-ACCORD) analysed findings from 13 US and Canadian studies. Their
aims was to determine incidence of anal cancer in HIV-positive patients, who
were divided into three categories – MSM, other men and women.
Rates of anal cancer
in these HIV-positive patients were compared to those observed in HIV-negative
men and women. Analyses were also conducted to see if there were temporal
trends in anal cancer incidence, and if any specific risk factors for the
malignancy in HIV-positive patients could be identified.
A total of 34,000
HIV-positive patients (55% MSM, 19% other men, 26% women) and 110,000
HIV-negative controls (90% men) were included in the study.
Data gathered between
1996 (the year effective HIV therapy first became available) and 2007 were
examined by the investigators.
Incidence of anal
cancer in MSM was 131 per 100,000 patient years. Among HIV-positive other men
incidence of the malignancy was 46 per 100,000 years, and incidence in
HIV-positive women was 30 per 100,000 person years. Incidence was therefore
significantly higher in HIV-positive MSM compared to other men (p < 0.01).
However, incidence rates for HIV-positive other men and women did not differ
Over the same period,
the incidence of anal cancer in HIV-negative men was just 2 per 100,000 person
years. There were no cases of the malignancy in HIV-negative women.
calculated that the risk of anal cancer was 80-times higher for HIV-positive
gay men compared to HIV-negative men (RR = 80.3; 95% CI, 42.7-151.1).
HIV-positive other men were almost 27 times more likely to develop anal cancer
compared to HIV-negative men (RR = 26.7; 95% CI, 11.5-61.7).
“Our finding of high
anal cancer incidence rates in HIV-infected MSM, other men, and women suggests
the need for enhanced primary and secondary prevention efforts among all
HIV-infected persons, as opposed to a targeted approach,” write the authors
Incidence of anal
cancer increased significantly in HIV-positive gay men between 1996-99 and
2000-2003 (p < 0.03). However, new cases of the malignancy then stabilised.
A similar trend was observed in HIV-positive other men and women. The
investigators suggest that the initial increase was a function of the improved
prognosis of HIV-positive patients, which allowed long-term cell changes caused
by high-risk strains of human papilloma virus to become cancerous. In contrast,
the levelling of cancer rate was attributed to the beneficial effects of
antiretroviral treatment on the immune system.
HIV-positive MSM were
significantly more likely to develop anal cancer than other HIV-positive men
(RR = 3.3; 95% CI, 1.8-6.0). The risk of the cancer was near identical for
HIV-positive other men and women.
Other risk factors for
the malignancy included older age (RR per additional ten years = 1.3; 95% CI,
A higher baseline CD4
cell count was protective against the development of the cancer (RR CD4 cell
count above 500 cells/mm3 vs. 200 cells/mm3 = 0.2; 95%
There is currently
disagreement about the value of anal cancer screening for HIV-positive
patients. However, the investigators suggest that this is likely to be cost
effective. They note “the New York State AIDS Institute guidelines…recommend
anal digital rectal examination for all patients, anal targeted anal cytology
for MSM, for individuals with a history of anogenital warts, and for women with
a history of abnormal cervical or vulvar histology.”