RE:Clinical Trial Size in Orphan and Rare Diseases Squamous cell carcinoma of the anus (SCCA) is a rare tumor.
https://ascopubs.org/doi/full/10.1200/EDBK_237433#:~:text=Anal%20squamous%20cell%20carcinoma%20(SCCA)%20has%20historically%20been%20considered%20a,world%20by%202.2%25%20per%20year.