Trends in epidemiology and primary treatment of anal squamous cell carcinoma in the Netherlands (1990-2021)

A rapid increase in the incidence of anal squamous cell carcinoma (SCC) was reported in several countries over the past decades. This study assessed trends in epidemiology and primary treatment over a 32-year period (1990-2021) using the Netherlands Cancer Registry. The study population included 4273 patients, 44.2% male and 55.8% female (median age 63 years). The age-standardised incidence rate (European Standardised Rate, ESR) increased from 0.5 to 1.6 per 100,000, which entailed an average annual percentage change (AAPC) of 5.0% (95% confidence interval [CI]: 4.5%-5.8%). While incidence among females increased continuously over the total period (AAPC 4.9%; 95%CI: 4.4%-5.6%), to 1.8 per 100,000 ESR in 2021, incidence among males increased until 2016 (annual percentage change [APC] of 6.3%; 95%CI: 5.6%-10.7%), after which it seemed to stabilise (APC -2.1%; 95%CI: -16.8%-4.5%). Significant trends were also observed in distribution of age, tumour stage and primary treatment modalities. Five-year relative survival (RS) was estimated using the Pohar-Perme estimator, and this improved from 56.1% in 1990-1997 (95%CI: 49.3%-62.4%) to 67.9% in 2014-2021 (95%CI: 64.7%-70.9%), but remained poor for stage IV disease. Evaluation through a multivariable Poisson regression model demonstrated diagnosis in the most recent period to be independently associated with better RS, in addition to female sex, younger age, early disease stage and any treatment. In conclusion, the rising incidence of anal SCC seems to decline in males, but not in females, and advances in diagnostics and therapeutic management have likely contributed to improved prognosis.