The men's study, presented at
an oral session, looked at prevalence of and risk factors for high-grade or
stage 2 to 3 anal intraepithelial neoplasia
(AIN) or anal cancer (carcinoma in situ) among HIV-positive MSM.
The researchers assessed the accuracy of
HPV PCR testing for more than a dozen high- and low-risk types, cytology
(testing for cell abnormalities, as done with a Pap smear) and anoscopy
(examination of anal-rectal tissue with a magnifying device). They also
compared anoscope-guided cytology vs cytology samples taken with swab.
The analysis included 103 participants in a prospective
cohort study that screened HIV-positive MSM for anal dysplasia from April 2010
through to September 2012 using all three methods.
The average age was 36 years and the mean and nadir
(lowest-ever) CD4 T-cell counts were 645 and 387 cells/mm3,
respectively, indicating well-preserved immune function. Most (85%) used
antiretroviral therapy (ART). Half were smokers – a known risk factors for HPV-related
cancer – and about 40% had anal warts. All the men reported anal sex, they had
a median of 1.5 sexual partners during the study, and 70% said they used
Overall, the researchers found that one-third to one-half of
the men had low-grade squamous intraepithelial lesions (LSIL) or stage 1 AIN,
and around 5 to 10% had high-grade squamous intraepithelial lesions (HSIL) or
stage 2 to 3 AIN, depending on the method used:
- Atypical squamous cells of undetermined significance (ASCUS):
Cytology with anoscope:
In a univariate analysis looking at separate risk factors,
older age and infection with HPV types 6, 39 or 42 predicted high-grade AIN or
anal cancer. However, in a multivariate analysis HPV 36 was the only
independent risk factor to reach statistical significance, conferring more than
a ten-fold higher risk (odds ratio 10.51; p=0.04). Neither smoking nor CD4
count were associated with greater risk in this study, in which CD4 cells were
For each testing method, the researchers calculated sensitivity
(ability to detect true cases), specificity (ability to rule out if not
present), positive predictive value (PPV, or proportion of correct positive
diagnoses) and negative predictive value (NPV, or proportion of correct
- Anal swab cytology: 94%, 42%, 31% and 97%,
- Cytology with anoscope: 90%, 61%, 40% and 96%,
- High-risk HPV testing: 83%, 15%, 24% and 77%,
- Anal swab cytology and high-risk HPV: 79%, 41%,
28% and 88%, respectively.
- Anal swab cytology and/or high-risk HPV: 100%,
15%, 24% and 100% NVP.
HIV-positive MSM cohort, the association of the oncogenic HPV genotype 39 with
other [high risk] HPV genotypes was the main risk factor associated with
high-grade AIN and/or carcinoma in situ," the researchers concluded.
With regard to
testing methods, "anoscopy-guided cytology does not improve the diagnosis
of the dysplastic lesions, and for this reason, we do not think that it should
be included in the screening protocol."
"should be systematically tested for dysplastic lesions with anal cytology
and HPV PCR," they summarised.
If cytology is
abnormal, irrespective of the grade of dysplasia, histologic evaluation of the
lesion should be performed using anoscopy, they added. But if cytology is
normal, HPV PCR screening should be done, and if high-risk HPV is found, the
patient should also be referred for anoscopy.
Asked if anal
screening could be done less often after a series of negative tests (as is the
case for HIV-negative women undergoing cervical screening), Hidalgo Tenorio said she
recommends ongoing screening every year for this population.
Judith Aberg asked about the unexpectedly high rate of HPV 39, speculating
whether vaccination against HPV types 16 and 18 might allow other types to take
over as major causes of cancer. Hidalgo Tenorio did not have an answer, but to
date HPV vaccines have mostly been given to young women, and more recently
young men, so coverage is likely still low in this population of MSM. She noted
that new vaccines are under study that will protect against more HPV types.