Prevalence of immune-related adverse events and anti-tumor efficacy in advanced/metastatic urothelial carcinoma following immune-checkpoint inhibitor treatment

Purpose We evaluated the prevalence of immune-related adverse events and anti-tumor efficacy in advanced/metastatic urothelial carcinoma following immune-checkpoint inhibitors (ICIs) treatment. Methods We conducted a multicenter retrospective study of patients with advanced/metastatic urothelial carcinoma treated with ICIs in four Spanish institutions. irAEs were classified using Common Terminology Criteria for Adverse Event (CTCAE) v.5.0 guidelines. The primary endpoint was overall survival (OS). Other endpoints were overall response rate (ORR) and progression-free survival (PFS). irAEs were evaluated as a time-dependent covariate to avoid immortal time bias. Results A total of 114 patients were treated with ICIs between May 2013 and May 2019, 105 (92%) of whom received ICIs as monotherapy. irAEs of any grade were experienced in 56 (49%) patients and 21 (18%) patients had grade ≥ 3 toxicity. The most frequent irAEs were gastrointestinal and dermatological toxicities, reported in 25 (22%) and 20 (17%) patients, respectively. Patients with grade 1–2 irAEs had significantly longer OS compared to those without grade 1–2 irAEs (median 18.2 vs. 8.7 months, HR = 0.61 [95% CI 0.39–0.95], p = 0.03). No association with efficacy was observed for patients with grade ≥ 3 irAEs. No difference in PFS was observed after adjusting for the immortal time bias. ORR was higher in patients who developed irAEs (48% vs 17%, p < 0.001). Conclusions Our findings suggest that development of irAEs was associated with higher ORR, and patients who developed grade 1–2 irAEs had longer OS. Prospective studies are necessary to confirm our findings.