Enfortumab vedotin (EV) related cutaneous toxicity to predict metabolic response on fluorodeoxyglucose (FDG)-positron emission tomography (PET) scan in advanced urothelial carcinoma (aUC): A single-center experience.

736 Background: EV is an antibody–drug conjugate approved for aUC after chemotherapy and immune checkpoint inhibitors. Cutaneous toxicity is the most frequent adverse event (AE) of EV, but the correlation between cutaneous toxicity and treatment efficacy based on standardized FDG-PET computed tomography (CT) assessment has not yet been established. Methods: In this retrospective single-center study, data from patients (pts) with aUC treated with more than one dose of EV after platinum-based chemotherapy and immunotherapy between September 2021 and August 2025 were analyzed. Treatment response was assessed by FDG-PET performed 3 months after treatment initiation. All the PET CT scans were reviewed in a blinded fashion by two readers using standardized criteria. The aim of this study was to establish a correlation between EV-related cutaneous toxicity and metabolic response. Results: Seventy-four pts were included. The median age of the population was 69.5 years, 86.5 % were male. Lymph-nodes were the most common site of metastasis (68.9%). Starting dose of EV was 1.25 mg/kg for 83.8% of the pts. The overall metabolic response on FDG-PET CT was 55.4% (41 pts), with a median duration of response of 5.23 (3.73–8.00) months. EV-related cutaneous toxicity occurred in 42 pts (56.8%), predominantly grade 1 (73.8%) and grade 2 (21.4%). No grade 4 or 5 AEs were reported. Logistic regression confirmed a correlation between cutaneous toxicity and metabolic response (Odds Ratio 8.17; 95% CI 2.87–23.32; p < 0.001). Among the 14 pts that achieved a metabolic complete response (CR), 13 experienced cutaneous toxicity (7 pts grade 1 and 4 pts grade 2). Two pts with grade 3 toxicity achieved CR. Progression-free survival was also significantly longer in pts with cutaneous toxicity (7.45 vs. 4.51 months; p < 0.001). Conclusions: These findings support a correlation between EV-related cutaneous toxicity in urothelial carcinoma and metabolic response on FDG-PET. These data should be confirmed in prospective trials.