The incidence of squamous cell carcinoma (SCC) of the anus and peri-anus is approximately one-tenth of that of the equivalent cervical cancer.  In Australia as elsewhere, epidemiological evidence has shown high risk groups to be HIV-positive men who have sex with men and other immune suppressed patients, but the majority of cases overall is immune-competent women.

Anal SCC can be treated with curative intent by chemoradiation without resorting to radical surgery.  However, survival and quality of life is significantly improved when disease is detected at an earlier stage.  As with cervical neoplasia, further benefit stands to be gained by detection and ablative treatment of high-grade pre-invasive lesions (“HGAIN”), although level 1 evidence for cancer incidence reduction and/or survival benefit is still forthcoming.¹

In the meantime, there is a need to define cost-effective screening protocols for high-risk groups.  In the case of women, this would logically be directed at those who are known to have been exposed to high-risk HPV, namely women with a history of HPV-related gynaecological neoplasia.  In a pilot screening study of Tasmanian women being followed up in colposcopy and gynaecological oncology clinics,² 40% of women had some degree of anal cytological abnormality (ASIL) necessitating high resolution anoscopy (HRA), biopsy and, where indicated, ablative treatment of HGAIN lesions.  The accuracy of cytology was further enhanced by high-risk HPV testing.

This study also confirmed other predictors of ASIL, such as age, smoking and inflammatory bowel disease.  One novel finding was the association with perineal hygiene practices.  Such associations may potentially inform screening protocols, as well as clinical practice and patient counselling.

Going forward, a randomised control trial is warranted to optimally evaluate the cost-effectiveness of opportunistic anal screening in women.  This could be conducted in parallel with the renewed National Cervical Screening Program.

While polyvalent HPV vaccines delivered in early adolescence may ultimately diminish the relevance of early detection, there will still be a considerable tail of unvaccinated women, as well as new arrivals who were not exposed to the vaccination program.  This reiterates the importance of targeted cost-effective screening.