His research focus is Genito-Urinary Oncology. He is former chairman of the EORTC Group Chemotherapy Subcommittee and initiated and led randomized studies in testicular cancer, prostate, renal and bladder cancer. He co-chaired phase 3 registration trials, ranging from chemotherapy and AR targeted agents in prostate cancer, to checkpoint inhibition (PD-1) trials in bladder cancer. He is involved in a wide variety of ongoing clinical studies, was the principal investigator for the practice changing phase 3 CARD study, and serves on Industry Advisory Board Committees, as well as Data Monitoring Committees. Prof de Wit is collaborating with the Departments of Urology and Translational Pathology in preclinicap and clinical translational research. He launched and is Chairman of the Dutch Uro-Oncology Study Group, comprising 27 Academic and supraregional Hospitals in the Netherlands. His publications include over 350 papers and book chapters.