Anal cancer: a 20-year retrospective study from Australia

Backgrounds: Anal cancer is an uncommon condition, occurring at higher rates in specific subpopulations. Clinical experience is limited and substantial changes have recently occurred in our understanding of this condition. We, therefore, set out to characterize patients presenting with anal cancer and investigate whether there have been any changes over the past 20 years. Methods: Retrospective audit of cases identified from pathology and clinical databases during the period 1 January 2000 to 31 December 2019. Results: Two hundred and sixteen patients had anal squamous cell carcinomas, comprising 160 (74%) males and 56 (26%) females. Mean age at initial diagnosis was 55.1 +/- 11.20 for males and 60.6 +/- 15.18 for females (P = 0.02). At initial diagnosis, HIV-positive cases were significantly younger than HIV negative cases (mean 52.2 +/- 9.35 vs. 62.8 +/- 11.61, P < 0.001); 46% of cases were classified as intra-anal, 29% perianal and 25% both; 52% were > 2 cm at diagnosis. At presentation, intra-anal cases were larger and more advanced than perianal cases (P = 0.049). Compared with the period 2000-2009, anal cancers presented more commonly in 2010-2019 (148 vs. 76), were more likely to occur in HIV-negative people and to be diagnosed at a similar stage. Conclusion: The number of anal cancer cases almost doubled over the study period and people living with HIV presented 10 years younger than others. Perianal cases presented earlier than those originating in intra-anal locations. Together with the large size at diagnosis, this suggests the potential value of screening, particularly for intra-anal cancers in those at high risk.