Although there are extensive guidelines on Anal SCC, the most recent being: American Society of Colon and Rectal Surgeons, Association of Coloproctology in Great Britain and Ireland and the joint guidelines of the European Society of Medical and Surgical Oncology, there is little consensus on the best practice in the treatment of AIN. Recommendations for the treatment and surveillance of AIN are often based on poor clinical evidence with much discrepancy.
The guidelines have also significantly changed since they were compared and contrasted in this great paper by Alam et al (2016). In the UK, The ACPGBI guidelines in 2011 were encouraging of High Resolution Anoscopy (HRA) in high volumes centres and gave a preference for 5% imiquimod as a treatment for AIN3 and 1% Cidofovir in female patients with Genitourinary Intraepithelial Neoplasia. They also recommended Photodynamic therapy and Ablative therapies such as electrocautery and Laser treatment as possible treatment modalities. Anal mapping was also advocated after a diagnosis of AIN.
This is quite different to the ACPGBI guidelines in 2017 which downgraded the importance of anal mapping due to futility and patient experience, were less enthusiastic about the benefits of HRA and, with the exception of HIV positive MSM where they suggested electrocautery may be the optimal treatment, they did not recommend a particular AIN treatment modality. They also had a new recommendation that all high grade AIN patients should be discussed at a specialist Anal SCC MDT.
The 2008 ASCRS guidelines recommended the treatment of AIN in all stages by either 5% Imiquimod, 5% Fluorouracil, targeted surgical destruction or Photodynamic therapy. There were no recommendations on High Resolution Anoscopy. The current ASCRS 2018 guidelines restricts ablative treatments to High Grade AIN only and recommends HRA in high risk populations when experienced practitioners are available. Unlike in the UK, ASCRS 2018 guidelines recommend the use of cytology for the diagnosis of AIN but recommends adding in HPV serology and p16 status.
Overall, there are 7 guidelines available for review in the literature, from 5 different countries between 2011 – 2018. Most recommend that screening could be beneficial to high risk populations, however there is insufficient evidence to suggest screening prevents malignancy. Guidelines from European countries recommend surgical excision (where possible) as the first line treatment, this conflicts with USA guidelines which prefer ablative or topical treatments. Except for one UK guideline that recommends the use of Imiquimod in lesions too large for surgical resection, no guideline expressed a strong preference for a specific AIN treatment.