Second-line Pembrolizumab for Metastatic Urothelial Carcinoma: Differences in Treatment Outcomes According to the Primary Site

Background/Aim: To evaluate the difference in the clinical efficacy and safety of pembrolizumab between patients with metastatic upper tract urothelial carcinoma (UTUC), which includes renal pelvic urothelial carcinoma (UC) and ureteral UC, and those with metastatic lower tract urothelial carcinoma (LTUC). Patients and Methods: A total of 752 patients who received pembrolizumab for the treatment of chemoresistant UC were retrospectively analyzed. We compared progression-free survival (PFS), overall survival (OS) and adverse events (AEs) in patients with renal pelvic UC, ureteral UC, and LTUC. Results: The median follow-up period was 42.5 [interquartile range (IQR)=35.1-47.4] months. The primary tumor site was in the upper tract in 362 (48.1%) patients [renal pelvis, n=219 (60.5%); ureter, n=143 (39.5%)] and in the lower tract in 390 (51.9%) patients. The estimated glomerular filtration rate before pembrolizumab treatment in the UTUC group was significantly lower than that in the LTUC group (p<0.001). The median PFS in the UTUC and LTUC groups was 3.4 months, respectively (p=0.271). The median OS in the UTUC and LTUC groups was 10.1 months and 11.7 months, respectively (p=0.195). In an analysis of UTUC divided into renal pelvic UC, ureteral UC, and LTUC, patients with renal pelvic UC had a significantly poorer prognosis in comparison to the other two groups (p=0.041). The incidence of any-grade AEs (51.7% vs. 47.9%, p=0.343) and grade ≥3 AEs (12.2% vs. 12.8%, p=0.826) in the two groups was not statistically significantly different. Conclusion: No significant differences were found between the UTUC and LTUC groups with regard to the oncological outcomes and safety of pembrolizumab. Patients with renal pelvic UC had a significantly poorer prognosis than those with other ureteral UCs and LTUCs.