Avelumab Maintenance Therapy for Advanced or Metastatic Urothelial Carcinoma

St Bartholomew's Hospital, Queen Mary University of London, Samsung Medical Center, Sungkyunkwan University, Clinique Victor Hugo, Centre Jean Bernard, Azienda Ospedaliera S.Maria, Hospital Universitario Virgen del Rocío, Karolinska University Hospital, Macquarie University, General University Hospital of Patras, Oncology Institute of Vojvodina, Universitair Ziekenhuis Brussel, Karolinska Institutet, Institut Gustave Roussy, Université Paris-Saclay, Inserm, University Health Network, Princess Margaret Cancer Centre, Yamagata University, State Healthcare Institution "Regional Clinical Oncological Dispensary", Weill Cornell Medicine, Cornell University, Virginia Cancer Institute, Yale Cancer Center, Pfizer (United States), University of Washington, Pfizer (Italy), Cancer Research Center, Seattle Cancer Care Alliance, Fred Hutch Cancer Center