Complete response to pembrolizumab in mismatch repair-deficient urothelial carcinoma with local recurrence and recurrent upper tract urothelial carcinoma: a case report.

Clinical evidence supporting the use of PD-1/PD-L1 inhibitors in treating urothelial carcinoma with microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) remains limited. We report a case of 77-year-old male with a history of multiple cancers. Immunohistochemical staining of bladder tumor revealed the loss of MSH2 and MSH6 expression, and MSI-H by PCR-based method and pathogenic alterations in MSH2 and MSH6 genes by next generation sequencing were confirmed, suggesting Lynch syndrome. He received pembrolizumab for local recurrence after total pelvic exenteration and recurrent upper tract urothelial carcinoma, and achieved complete remission. This case supports the potential of PD-1/PD-L1 inhibitors as a promising treatment option for MSI-H or dMMR urothelial carcinoma, similar to other solid tumors with MSI-H or dMMR.