OBJECTIVES Economic impact of prostate cancer is increasing in relation to its increased incidence and increased patient survival. Clinical trials are essential to evaluate the efficacy and safety of new treatments but may also result in economic benefits by avoiding the cost of the drug. Our objective is to determine the avoided cost in investigational drugs in clinical trials of prostate cancer conducted in a period of 18 years in a tertiary center. MATERIAL AND METHODS We carried out an observational of prevalence study with retrospective collected data of clinical trials involving currently marketed drugs and cost avoidance during the study period (1996-2013) was calculated. RESULTS We include in this review five clinical trials on prostate cancer that met selection criteria of 18 performed. All of them were phase III, multicenter, international and with current marketed drugs. 136 patients were included. Total cost avoidance of 696,002€ and an average cost avoidance by clinical trial of 139,200€ were obtained. Average cost avoidance per patient was 5,118€. CONCLUSION Cost avoidance in investigational drugs is a tangible benefit of clinical trials, whose realization is a source of economic benefits for the hospital, not only by directly generated by each trial. Clinical trials are an exceptional framework for progress in clinical research and real savings for the health system.