(UroToday.com) The Earlier Treatment in Prostate Cancer “How can we maximize the therapeutic index?” educational session at the European Society of Medical Oncology’s (ESMO) 2021 congress included a presentation by Nicolas Mottet discussing evidence-based treatment options in biochemically relapsed prostate cancer. Dr. Mottet notes that the definition of relapse after external beam radiotherapy is the nadir + 2 ng/mL, with the rationale for this being that it was the best definition to predict further metastases. It was initially based on the Phoenix consensus but later was considered as the main clinical definition of relapse. With regards to relapse after radical prostatectomy, Dr. Mottet notes that there is a major difference between PSA relapse (any PSA rise following an undetectable level) and a clinically significant PSA rise, which is the best predictor of further metastases. Post-radical prostatectomy, the definition of relapse is no longer a PSA of 0.2 ng/mL and rising. Currently, following an undetectable PSA (<0.1 ng/mL), the best PSA threshold to define a relapse is 0.4 ng/mL and rising (since 2018 EAU-ESTRO-SIOG-ESUR guideline), given that this is the best correlation with systemic progression; this definition has also been adapted as a consensus statement by ASCO. The threshold of PSA > 0.4 ng/mL and rising is the most clinically relevant threshold, but it is not the threshold to define relapse, and it is not the threshold to consider salvage treatment.