LAUSR

TPS157Background: Salvage radiotherapy (SRT) is as a potentially curative treatment for prostate cancer (CaP) patients presenting biochemical relapse after radical prostatectomy (RP). Metformin is a well-known antidiabetic drug that has demonstrated anti-cancer and radio-sensitizing effects. We aim to study whether metformin combined with SRT will improve cancer control by prolonging time to progression (TTP). Methods: This is a multicenter, randomized (1:1) phase II trial of SRT (70Gy/35fr to the prostate bed) with or without metformin (850mg BID for 52 wks) (NCT02945813). Metformin 850mg q.d. is started 4 wks prior to SRT. Stratification variables include Gleason score, PSA at randomization, surgical margin status and ADT use (allowed if PSA > 0.5, R0, post-RP PSA-DT 12 wks before registration; PSA progression after RP defined as 2 consecutive rises with final PSA > 0.1 ng/mL or 3...