Comparison of Oncological Outcomes of Pembrolizumab as Second-line Therapy and Maintenance Avelumab Therapy in Advanced Urothelial Carcinoma After Platinum-based Chemotherapy

Background/Aim: Sequential therapy using chemotherapy and subsequent immune checkpoint inhibitor (ICI) treatment prolongs the survival of patients with advanced urothelial carcinoma (UC). However, no comparison data for oncological outcome between pembrolizumab and avelumab has been reported. Thus, we compared oncological outcomes between pembrolizumab as second-line therapy and maintenance avelumab therapy in patients with advanced UC. Patients and Methods: We retrospectively evaluated patients with advanced UC treated with pembrolizumab or avelumab between January 2018 and February 2023. We compared oncological outcomes after adjusting for patient characteristics. Immune-related adverse events (AEs) in each group were evaluated using the Common Terminology Criteria for Adverse Events. Results: There were 186 and 44 patients in the pembrolizumab- and avelumab-treated cohorts, respectively. After propensity score matching, 43 patients from each group were selected and analyzed. Median progression-free survival from the initiation of pembrolizumab and avelumab treatments was 126 and 139 days, respectively (log-rank test, p=0.625). Median overall survival in the pembrolizumab and avelumab cohorts were 658 days and not reached, respectively (log-rank test, p=0.249). Thirty-eight (20.4%) and 14 (31.8%) all-grade immune-related AEs were observed in 186 pembrolizumab- and 44 avelumab-treated patients, respectively (chi-squared test, p=0.112). Regarding endocrine-related AEs, 12 (6.5%) and none (0%) were observed in pembrolizumab- and avelumab-treated patients, respectively (Fisher’s exact probability test, p=0.129). Conclusion: Pembrolizumab and maintenance avelumab therapy provide equivalent oncological outcomes in patients with advanced UC. Although no significant difference was observed, there might be a potential risk of higher endocrine-related AEs due to pembrolizumab compared to avelumab maintenance therapy.