This question continues to be a vexing one with our definitive answers coming in probably 5 years time. There is increasing evidence that AIN3 is a precursor to anal cancer but the problem is that we can screen for AIN3 (anal cytology, high resolution anoscopy) BUT we don't know two fundamental pieces of information.
1) How do we treat AIN3 effectively? To date, we have seen many treatment modalities trialed but AIN 3 is highly recurrent. A triple arm trial in 146 HIV+ MSM reported by Dr. De Vries examined a group of HIV+ MSM who were screened by high resolution anoscopy and histopathologically confirmed to have AIN. He then randomized them into 3 groups (16 weeks of imiquimod, 16 weeks of 5-FU or 16 weeks of monthly electrocautery). It was disappointing to see that recurrence rates were high for all patients at 72 weeks (67%), imiquimod users (72%), 5FU users (58%) and electrocautery (68%). When stratified by perianal vs. intraanal lesions, the peri-anal lesions did better.
2) Which men with AIN 3 should we treat? As Dr. Mary Poynthn from the SPANC team demonstrated, nearly half of HIV+ MSM had detectable high-grad SIL (HSIL) and there was a high regression rate for AIN3 (~39 per 100 person years). These figures almost match the "success rates" of many treatment modalities. We need better tools to distinguish the AIN3 that are more likely to progress onto anal cancer (e.g. use of biomarkers like E6/7?).
Until the above 2 questions are answered, I would not suggest implementation of anal cancer screening using anal cytology/HRA. The alternative is to undergo tertiary screening (i.e. early cancer detection) through regular DARE for those at highest risk (HIV+ MSM who have 100 times greater incidence rates compared to the general population) until more evidence is established for anal cancer screening.