C-Reactive Protein-Albumin Ratio Predicts Objective Response to Enfortumab Vedotin in Metastatic Urothelial Carcinoma

Background: Enfortumab vedotin (EV), an antibody-drug conjugate that targets Nectin-4, is used for patients with metastatic urothelial carcinoma who have experienced progression on platinum-based chemotherapy and checkpoint inhibitors. Despite the widespread use of the drug, evidence remains scarce regarding clinical indicators that can predict the response to EV treatment. Objective: We aimed to explore the predictive value of clinical indicators derived from peripheral blood tests for treatment responses to EV. Methods: We utilized records of 109 patients with metastatic urothelial carcinoma treated by EV from our multi-institutional dataset. Receiver operating characteristic curve analyses for predicting objective responses including several indicators from blood examinations, such as C-reactive protein-albumin ratio (CAR), hemoglobin, neutrophil-lymphocyte ratio, platelet-lymphocyte ratio, and lactate dehydrogenase, were performed. The optimal cutoff points were determined by the Youden index. Logistic regression analyses for achieving objective responses to EV treatment were performed among these indicators. Results: The median age of the cohort was 74 years, and the median follow-up duration was 10 months for the entire group. Median overall survival and progression-free survival from the initiation of EV were 12 and 6 months, respectively. The objective response rate and disease control rate were 48% and 70%, respectively. The receiver operating characteristic curve analysis aimed at predicting the achievement of an objective response to EV showed that the concordant index for the CAR was 0.774, significantly surpassing other indicators such as hemoglobin level, neutrophil-lymphocyte ratio, platelet-lymphocyte ratio, and serum lactate dehydrogenase. The Youden index identified an optimal cutoff value of 1 for CAR (mg/L for C-reactive protein and g/dL for serum albumin level) in predicting the objective response to EV treatment. Using the cutoff value for the CAR, the cohort was divided into 32 patients (29%) with lower CAR and 77 patients (71%) with higher CAR. The objective response rate was observed to be 84% in the lower CAR group and 32% in the higher CAR group (p < 0.0001). A logistic regression analysis revealed that an Eastern Cooperative Oncology Group Performance Status ≥1 (p = 0.04) and a CAR ≥1 (p < 0.001) were identified as independent predictors for the objective response to EV. Conclusions: The evaluation of the CAR from a concise blood examination at the initiation of EV could effectively predict the treatment response to EV in patients with metastatic urothelial carcinoma after the progression of platinum-based chemotherapy and checkpoint inhibitors.