Very high incidence of high-grade pre-cancerous anal lesions among young HIV-positive Thai gay men

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Approximately a third of HIV-positive gay men in Thailand developed high-grade pre-cancerous anal lesions during just one year of follow-up, investigators report in the online edition of AIDS. Infection with high-risk strains of human papillomavirus (HPV) was an important risk factor for the development of high-grade lesions. The investigators were extremely concerned by their findings and recommend that healthcare providers, policy makers and communities of gay men will need to make plans for screening and treating pre-cancerous anal lesions.

HIV-positive gay men are the group most affected by anal cancer. The malignancy is preceded by anal lesions (anal intraepithelial neoplasia, AIN), which are usually associated with infection with high-risk strains of HPV.

Little is known about the prevalence and incidence of high-grade precancerous anal lesions (HGAIN) among gay men in low- and middle-income settings.



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

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.


A variant characterised by a specific genotype.


prospective study

A type of longitudinal study in which people join the study and information is then collected on them for several weeks, months or years. 

anal intraepithelial neoplasia (AIN)

An abnormal growth on the surface of the rectum or anal canal which, when observed with a microscope, suggests that the cells could be malignant (cancerous).

An international team of investigators therefore designed a prospective study involving 123 HIV-positive and 123 HIV-negative gay men in Bangkok, Thailand.

They were screened for anal lesions at baseline and again after six and twelve months. The participants also provided samples for anal cytology to determine the prevalence and persistence of infection with high-risk HPV strains (HPV 16/18).

The participants had a median baseline age of 28 years. The HIV-positive participants had a median baseline CD4 cell count of 343 cells/mm3. Only 13% of HIV-infected participants were taking antiretroviral therapy when the study started and 10% had an undetectable viral load. At the end of the study, the proportion of HIV-positive participants taking antiretrovirals had increased to 47%, and at the end of the study some 33% had an undetectable viral load and median CD4 cell count was 277 cells/mm3.

Baseline prevalence of high-grade pre-cancerous anal lesions was 19% among the men with HIV and 11% in the HIV-negative men.

During follow-up, 27% of HIV-positive men without HGAIN at baseline had developed pre-cancerous anal lesions, as had 7% of HIV-negative men.

The probability of having high-grade pre-cancerous anal lesions at month twelve was 29% for HIV-positive men to 8% for HIV-negative participants (p = 0.001).

Analysis of men with low-grade anal lesions at baseline showed that 33% of those with HIV and 13% of HIV-negative individuals progressed had HGAIN after twelve months of follow-up.

Anal infection with any strain of HPV was detected in 85% of HIV-positive and 59% of HIV-negative participants (p < 0.0001).

HIV-positive men were significantly more likely to be infected with a high-risk HPV strain than the HIV-negative men (58 vs 37%, p = 0.001).

Persistent high risk HPV infection was found in 47% of HIV-positive and 19% of HIV-negative participants.

Infection with HIV was associated with a more than three-fold increase in the risk of developing high-grade pre-cancerous anal lesions (HR = 3.26; 95% CI, 1.31-8.14; p = 0.011).

“MSM [men who have sex with men] with HIV infection in our study had approximately 2-3 times higher relative risk for incident HGAIN,” comment the authors. They believe this indicates “a role for immunodeficiency and/or HIV-HPV interactions in the development of HGAIN”.

Persistent infection with HPV 16/18 increased the risk of incident HGAIN by a factor of five (HR = 5.16; 95% CI, 1.89-14.08; p < 0.001).

“The high prevalence and incidence of HGAIN in our young MSM cohort is of great concern,” conclude the investigators, who note that as many as 15% of men with high-grade pre-cancerous anal lesions progress to anal cancer within three to five years. “Practitioners, policy makers, and communities will need to plan for strategies to screen for treat AIN using data available from their own setting.”


Phanuphak N et al. High prevalence and incidence of high-grade anal intraepithelial neoplasia among young Thai men who have sex with men with and without HIV. AIDS 27, online edition: DOI: 10.1097/QAD.0b013e328360a509, 2013.