We used the patterns of recurrence on 18F-fluciclovine PET/CT in post-prostatectomy patients enrolled in the XXXX trial to evaluate how well the most recent NRG Oncology and Groupe Francophone de Radiothérapie Urologique (GFRU) contouring recommendations encompassed all sites of recurrence in the prostate fossa and pelvic nodes in comparison to former Radiation Therapy Oncology Group (RTOG) recommendations.