Background: Radical prostatectomy (RP) is recommended as a standard treatment for localized prostate cancer. However no recommendations exist for pts with detectable PSA after RP. Methods: Pts with localized prostate cancer, treated by RP (R0 or R1), with a PSA level post-RP ≥ 0.2 ng/mL and ≤ 2 ng/mL at randomization and N0 M0 on imaging were included. Pts were randomized (1:1) to radiotherapy (RT) alone (RT arm) or 6 months degarelix hormone therapy (HT) with RT (RT+HT arm). RT consisted of pelvic irradiation (46 Gy in 23 Fr) with a boost on the prostate bed (66 Gy in 33 Fr). The primary endpoint is the event-free survival (EFS). Secondary endpoints are: 5-yr EFS and metastases-free survival, 5 and 10-yr OS, acute and late toxicity (CTCAE V4.0), and QOL. With 122 patients, the probability of selecting the most effective arm is over 80% for a 20% reduction in the HR = 0.80. Results: From Dec-2012 to Sept-2015, 125 pts were included (RT arm: 64 pts; RT+HT arm: 61). Median follow up is 14.7 months (6.2; 33.5). The baseline characteristics are well-balanced: median age was 66 yrs (50-77), all men having an ECOG ≤ 1 (ECOG 0 in 92%), a median Gleason score of 7 (3-9), a median PSA of 0.3 ng/mL (0.09-1.82) post-RP and 0.6 ng/mL (0.12-3.65) at randomization. All pts received 33 Fr of RT. In the RT+HT arm 98.4% of pts received the 6 months of HT planned. All pts were eligible for safety analysis. No grade 4 toxicity or toxic death was reported. Grade 3 acute toxicity, occurring within 6 months of RT, were reported for 11/125 pts (9%): 3/64 pts (5%) in the RT arm and 8/61 pts (13%) in RT+HT arm (NS). Regarding grade 3 toxicities, the following occurred only in the RT+HT arm: erectile dysfunction (3 pts) and urinary incontinence (2 pts); in contrast, dysuria/pollakiuria (2 pts) occurred only in the RT arm. In the RT+HT arm, grade 2 toxicities included hot flushes (8 pts) and decreased libido (7 pts). Conclusions: In terms of acute toxicities the RT+HT arm is well tolerated with the observed toxicities usually expected with concomitant HT. The primary endpoint analysis is expected for 2018. Clinical trial information: NCT01994239