Susanne Osanto, MD, PhD, from the Leiden University Medical Center, Leiden, Netherlands, discusses the clinical implications of circulating tumor cell (CTC) analysis in prostate cancer at the European Association of Urology (EAU) conference 2017 in London, UK. She argues that for patients with localized prostate cancer, there is currently no evidence that circulating tumor cells can be used in a clinical setting to monitor disease or treatment outcomes. In contrast, in patients with a higher tumor load, such as those with castration-resistant prostate cancer (CRPC) who need to undergo systemic treatment or in whom we know that treatment resistance has developed and patients need to be selected for targeted treatments, there is more evidence that CTCs can be used. However, she highlights that more data and prospective trials are needed to verify these findings. She concludes that the future is bright; while the clinical utility of CTCs is better proven in castration-resistant prostate cancer with high tumor burden, using CTCs, cell-free DNA or measurement of exosomes will be very important for selecting prostate cancer treatments in future.