Complete response to tislelizumab in a metastatic urothelial carcinoma after surgery associated with high tumor mutational burden: a case report

Metastatic urothelial carcinoma (mUC) is associated with poor prognosis. Cisplatin-based combination chemotherapy is the preferred initial regimen for patients with mUC. However, a substantial proportion of patients cannot receive cisplatin-based chemotherapy due to renal impairment or other comorbidities. Currently, immune checkpoint inhibitors (ICI) showed to be effective in cisplatin-ineligible mUC patients on first-line treatment. Tislelizumab is an anti-human programmed death receptor-1 monoclonal IgG4 antibody, which was specifically engineered to minimize binding to Fc gamma R on macrophages to abrogate antibody-dependent phagocytosis. But there is no report of tislelizumab as a first-line treatment for cisplatin-ineligible patients with mUC currently. Here, we report a cisplatin-ineligible mUC patient with PD-L1-negative, microsatellite stable (MSS), high tumor mutational burden (TMB-H) obtained complete response receiving tislelizumab therapy after laparoscopic debulking surgery. Progression-free survival has exceeded 16 months since treatment with tislelizumab. To our knowledge, this is the first reported case of cisplatin-ineligible mUC patient with PD-L1-negative, MSS and TMB-H who responded well to tislelizumab as a first-line treatment. However, we still need more studies to assess the efficacy of tislelizumab as a first-line treatment in cisplatin-ineligible mUC patients and to confirm predictive values of TMB for efficacy of tislelizumab.