Anal cancer incidence is high in populations at high risk, as HIV-infected men who have sex with men, receptive anal intercourse, and high risk sexual behaviour, warranting consideration of early detection approaches. HPV has been shown to be a major cause in the development of anal cancer: persistent infection with high-risk types of HPV causes more than 80% of anal cancers. In the precursor to anal cancer, anal intraepithelial neoplasia (AIN), the prevalence of HPV infection is high. There is no widely accepted procedure guidelines for men with possible exposure to HPV that can lead to dysplasia. The aim of this study is to determine the prevalence of HPV DNA and RNA, to lay the bases for a possible screening strategy for the prevention of anal cancer in high-risk populations.
We evaluated anal pap test and HPV infection, with both HPV genotyping and mRNA HPV tests, in 129 anal cytology samples collected at the center of the National Surveillance Network of Sexually Infections of Florence in the period 2015-2016, and sent to ISPO for the analyses. The specimens were collected in ThinPrep vials (Hologic). HPV typing was performed by reverse line hybridisation (Ampliquality HPV express AB analitica). Genotype analysis for HPV DNA was available for 52 samples. RNA analysis for E6/E7 HPV mRNA expression was available for 26 samples. The test was performed with Aptima HPV assay (Hologic) with Panther system, that qualitative detects 14 hr- HPV type. 27 samples were also tested for HR-HPV DNA by Cobas 4800 HPV test (Roche).
The prevalence of HPV infection is 78,8% if considering both high risk and low risk HPV types, and 57,7% if considering only hr types. The most prevalence type is HPV16 pos (26.8%), followed by HPV 45 (22%) and HPV 18 (19.5%). Multiple infections are frequent: more than 3 types are co-infecting in 25 samples. mRNA HPV was positive in 65.4%. All mRNA-negative samples have negative pap test or non valuable. Of the 45 samples with cytology ≥ ASC-us, 24 were tested for HPV Typing: 79,2% were positive for hr-types; 47.4% of these were HPV16-positive. Cobas HPV test results are concordant (100%) with typing results.
In order to establish a pilot screening programme for anal cancer, it is valuable to determine the prevalence of HPV types and the expression of viral oncogene E6/E7. Anal cytology has been used to predict those at risk of AIN, but the limited sensitivity restricts its usefulness as a potential screening technique. Completing HPV DNA e RNA analyses on all samples, and data from follow up on this group of patients will determine if HPV tests (DNA or RNA) can be applied in a screening contest for anal cancer prevention.