Neoadjuvant Immunotherapy for Muscle-Invasive Bladder Cancer

Background and Objectives: Facing neoadjuvant chemotherapy followed by surgery, neoadjuvant immunotherapy is an innovative concept in localized muscle-invasive bladder cancer. Herein, we performed a review of the available and ongoing evidence supporting immune checkpoint inhibitor (ICI) administration in the early stages of bladder cancer treatment. Materials and Methods: A literature search was performed on Medline and clinical trials databases, using the terms: "bladder cancer" OR "urothelial carcinoma", AND "neoadjuvant immunotherapy" OR "preoperative immunotherapy". We restricted our investigations to prospective clinical trials evaluating anti-PD-(L)1 and anti-CTLA-4 monoclonal antibodies. Data on efficacy, toxicity and potential biomarkers of response were retrieved. Results: The search identified 6 ICIs that were tested in the neoadjuvant setting for localized bladder cancer-4 anti-PD-(L)1 inhibitors (Pembrolizumab, Atezolizumab, Nivolumab and Durvalumab) and 2 anti-CTLA-4 inhibitors (Ipilimumab and Tremelimumab). Most of the existing literature was based on single-arm phase 2 clinical trials that included from 23 to 143 patients. The pathological complete response rate (pCR) and pathological response rate (pRR) ranged from 31% to 46% and from 55.9% to 66%, respectively. Survival data were immature at this time. The safety profile was acceptable, with severe treatment-related adverse events ranging from 6% to 41%. Conclusions: The results of early phase trials are encouraging, and more investigations are needed to strengthen the rationale for immune checkpoint inhibitor administration in localized muscle-invasive bladder cancer.