A radiological complete response to pembrolizumab in a patient with metastatic upper urinary tract urothelial cancer and Lynch syndrome

Introduction In Lynch syndrome, urothelial cancer is the third most common cancer, following colorectal and endometrial cancers. Little is known, however, about the efficacy of immune checkpoint inhibitors in the treatment of metastatic urothelial cancer in Lynch syndrome. Case presentation A 49‐year‐old patient with metastatic urothelial cancer underwent pembrolizumab therapy after platinum‐containing chemotherapy. The efficacy of the pembrolizumab therapy was good. Her lung and bone metastatic lesions disappeared in imaging studies and her back pain decreased dramatically. Pathogenic mutations of MSH2 and BRCA2 were found in the DNA extracted from her tumor, and subsequent genetic analysis confirmed the germline pathogenic variant of MSH2. As such, this case was genetically diagnosed as Lynch syndrome. Conclusion We report metastatic urothelial cancer in a patient with Lynch syndrome who demonstrated a radiological complete response to pembrolizumab therapy. Accurate genetic diagnosis can provide useful information to both the patient and their relatives.