Immunohistochemical Expression of p53 and FGFR3 Predicts Response to Enfortumab Vedotin in Metastatic Urothelial Carcinoma

Locally advanced or metastatic urothelial carcinoma is a genomically and molecularly heterogeneous disease associated with various clinical outcomes. We aimed to evaluate the association between the status of p53/FGFR3 expression and the efficacy of enfortumab vedotin (EV) in metastatic urothelial carcinoma. We evaluated the association between p53 (abnormal vs. wild-type) or FGFR3 (high vs. low) expression determined by immunohistochemistry and response to EV in 28 patients with metastatic urothelial carcinoma. Overall, 60.7% showed abnormal p53, and 17.9% had high FGFR3 expression. The rates of objective response to EV were statistically higher in patients with abnormal p53 than in those with wild-type p53 (<i>p</i> = 0.038). Patients with pure urothelial carcinoma (<i>n</i> = 18) and low FGFR3 showed significantly better response to EV than those with high FGFR3. When the statuses of p53 and FGFR3 were combined, abnormal p53/low FGFR3 (vs. wild-type p53/high FGFR3) was strongly associated with favorable outcomes in both the entire cohort (<i>p =</i> 0.002) and in cases of pure urothelial carcinoma only (<i>p</i> = 0.023). Immunohistochemically abnormal p53 tumors were found to respond well to EV, while high FGFR3 tumors had a poorer response. Thus, p53 and FGFR3 are potential biomarkers for predicting response to EV treatment in patients with urothelial carcinoma.