A Complete Response After Pseudo-progression: Pembrolizumab for Metastatic Squamous Cell Carcinoma (SCC) of the Bladder.

Bladder cancer is the sixth most common cancer in the United States, with over 80,000 new diagnoses and 17,000 deaths in 2019.1,2 At the time of diagnosis, urothelial carcinoma (UC) is the predominant histology (90%-95%), followed by squamous cell carcinoma (SCC) (3%-6.7%), and adenocarcinoma (AC) (1%).3-5 Metastatic SCC is an aggressive subtype of bladder cancer, with 2-year overall survival at only 27% compared with UC (44%) and has a tendency for muscular invasion.6,7 Given the rarity of bladder SCC, there is a lack of evidence guiding standard-of-care therapy in both the localized and metastatic settings.