First-line pembrolizumab therapy in a cisplatin-ineligible patient with plasmacytoid urothelial carcinoma: A case report.

Background Plasmacytoid urothelial carcinoma (PUC) is a rare but aggressive variant of transitional cell carcinoma. In patients with unresectable disease, cisplatin-based combination chemotherapy is the most commonly used treatment. However, many patients are cisplatin-ineligible due to poor performance status or other comorbidities. We report a case of a cisplatin-ineligible patient with metastatic PUC who was treated with pembrolizumab. Case report A 71-year-old man with 30 pack-year smoking history and schizoaffective disorder was found to have multiple right-sided lung nodules after presenting with atypical chest pain. Staging CT showed bilateral adrenal masses and a large soft tissue mass in the right iliac fossa. Tissue pathology and immunohistochemical staining was consistent with PUC. As the patient was cisplatin-ineligible due to poor performance status and multiple medical comorbidities, the decision was made to treat with pembrolizumab. Repeat CT chest and abdomen showed partial response at three months and stable disease at six months. Discussion The KEYNOTE-052 study found that first-line pembrolizumab in cisplatin-ineligible patients with urothelial cancer resulted in complete or partial response in 24% of patients with few adverse effects. However, it is unclear if patients with plasmacytoid variant were included. To our knowledge, this is the first case report of a patient with metastatic PUC not only treated with pembrolizumab but shown to have clinical response. Conclusion Given our patient's clinical response, pembrolizumab is a promising first-line agent for treating cisplatin-ineligible patients with metastatic PUC. Further evaluation is warranted to confirm the benefit of treating this patient population with pembrolizumab.