PARP inhibitors are used in the treatment of ovarian cancers, and have recently shown potential against prostate cancer. Joaquin Mateo, MD, from the Institute of Cancer Research and The Royal Marsden, London, UK talks to us about a Phase II clinical trial, TOPARP (NCT01682772), which examined the efficacy of the inhibitor olaparib in prostate cancer patients. Dr Mateo discusses the results of the trial and the plans to follow up this work with an expanded study, and tells us his expectations for the future of PARP inhibitors in the treatment of prostate cancer. This interview was recorded at the 2017 European Society for Medical Oncology (ESMO) in Madrid, Spain.