Clinical Outcomes of Mixed Response to Pembrolizumab in Advanced Urothelial Carcinoma After Platinum-based Chemotherapy.

Background/aim: Despite the presence of a mixed response (MR) in patients with urothelial carcinoma (UC) who receive immune checkpoint inhibitors, the clinical outcome of these patient has not been reported. We evaluated the clinical outcome of MR to pembrolizumab for advanced UC.

Patients And Methods: Advanced UC patients who received pembrolizumab after platinum-based chemotherapy failure with measurable disease in multiple organs were retrospectively analyzed.

Results: Among 31 patients, MR [including progressive disease (PD)+complete response (CR) or partial response (PR)] was confirmed in 4 (12.9%). The median overall survival (OS) of the CR+PR (including CR+SD±PR), stable disease (SD), PD (including PD±SD) and MR groups was 16.0, 5.1, 5.4 and 4.3 months, respectively. There was no significant difference in the OS between the MR and CR+PR response groups (log-rank test, p=0.069).

Conclusion: A mixed response to pembrolizumab in advanced UC was not uncommon. Despite the non-significant difference in the OS between the mixed and CR+PR response groups, the OS of the MR group tended to be similar to that of the SD and PD response groups.