Early detection of anal squamous cell carcinoma with the use of high resolution anoscopy.

Background: In the UK, few (12%) anal squamous cell carcinomas (aSCC) are diagnosed early at stage 1 (T1N0M0). The Homerton Anogenital Neoplasia Service (HANS) is a highly specialised tertiary centre where high resolution anoscopy (HRA) is performed to diagnose and treat anal intraepithelial neoplasia (AIN), a precursor to cancer. In some cases, aSCC (here defined as anal canal cancers and perianal cancers up to 5cm from the anal verge) is found on referral for AIN; in others, aSCC may develop while undergoing AIN management. We reviewed aSCC diagnoses at our specialist unit to establish whether HRA offers added value in the early detection of aSCC in a high-risk cohort.

Methods: A cross-sectional analysis was performed of all primary aSCC diagnoses at HANS between January 2016 and June 2021. Patient records, histopathology and radiology reports were reviewed to define anal cancer stage per TNM classification (AJCC version 8). Results were compared with national anal cancer data published by the Office for National Statistics (AJCC version 8).

Results: Fifty-three aSCC diagnoses were made at HANS; 35 (66%) were stage 1 (14 prevalent, 21 incident), 11 (21%) stage 2 (9 prevalent, 2 incident) and 6 (11%) stage 3 (5 prevalent, 1 incident). None were stage 4; 1 cancer was unstageable due to further management at another unit. By comparison, 5836 aSCCs were diagnosed in the UK between 2013-2017; of these, 12.0% were stage 1, 22.8% stage 2, 33.0% stage 3 and 8.46% stage 4; 23.8% were unknown or unstageable. There was a statistically significant difference in the proportion of early (i.e. stage 1) HRA-detected cancers (HDCs) compared with national statistics (p < 0.001).

Conclusion: Our results suggest that surveillance and examination within an HRA programme may lead to detection of aSCC at an earlier stage allowing for less morbid treatment and potentially a lower mortality.