Why are patients getting enzalutamide s/p prostatectomy not candidates for salvage radiation therapy?   

On the EMBARK trial (Freedland et al., NEJM 2023), 25% of men had a prostatectomy and the publication states  "Patients were excluded … if after radical prostatectomy they were considered by the investigator to be a candidate for salvage radiation therapy." Why was salvage radiation therapy excluded?