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Day 3 – Joint Symposium Session: Prevention of Anal Cancer in gay and Bisexual Men: The Current State-of-Play and Future Directions.
“What should we be doing for our patients now?” Dr Jason Ong, Monash University, The Alfred – Melbourne Sexual Health Centre, VIC, Australia
Dr Ong acknowledged the HPV vaccine as a game-changer in the prevention of HPV-associated anal cancer however there is still a cohort of males who remain unvaccinated and therefore will continue to be at risk of anal cancer for many years to come.
Many ask the question: if screening for cervical cancer using the PAP smear works so well in early detection of cervical pre-cancerous lesions, then why can’t we take this methodology and apply it to anal screening of MSM for pre-cancerous lesions (aka ‘CHAP smears’)?
Some similarities and differences between anal and cervical anatomy and lesions were described:
- Both have transformational zones
- HPV responsible for a significant proportion of pre-cancerous changes
- Pre-cancerous lesions are histologically similar
- The anal canal is a much larger area to swab (approx. 5cm tube)
- It is more difficult to visualise anal lesions
- Natural history of lesions between each site is different (up to 30% of anal smears are positive for abnormal changes)
- Progression of changes is different as many more anal intraepithelial neoplasia (AIN) resolve over time compared to cervical intraepithelial neoplasia (CIN)
- Different referral rates (only approx. 3% of cervical PAP smear result in onward referral for colposcopy but up to 60% of men undergoing anal screening would need referral due to the increased rate of high grade anal lesions. This has implications for the workforce as it does not have the capacity to deal with such a large volume of referral for anoscopy or further investigation).
High-grade anal intraepithelial neoplasia (HGAIN) regress at a rate of 36/100 person years so if left alone, many would disappear.
In answering the question of whether we should screen for early anal cancer, Dr Ong explained that the best annual screening tool for MSM would be the digital anorectal examination (DARE). As approx. 50% of anal cancers are externally visible and approx. 2.9cm in size, and due to the fact that many HGAIN resolve spontaneously over time without intervention, DARE is a most cost-effective and simple early detection technique.
In another study, Dr Ong also explored the acceptability of a DARE for men with favourable findings. 82% of men felt relaxed during the procedure and 99% were willing to have another DARE in a years time.
As a side note, Dr Ong will be conducting a teaching session on Friday 16th Nov from 10:30am-11:00am using his plastic bum segment for this wishing to perfect their DARE technique …sadly I will miss out!