A phase II Salvage Trial of AR Inhibition with ADT and Apalutamide with Radiation therapy followed by docetaxel in men with PSA recurrent prostate cancer (PC) after radical prostatectomy (STARTAR).

TPS5097 Background: Androgen deprivation combined with salvage external beam radiation therapy (RT) have improved survival for patients (pts) with non-metastatic hormone naïve PC and PSA recurrence after radical prostatectomy (RP). Our recent STREAM trial showed addition of enzalutamide to RT and ADT had a 3-year progression free survival (PFS) of 53%. Adding effective PC treatments in this setting may further improve 3-year PFS. Methods: STARTAR is an investigator-initiated phase 2 trial for salvage treatment of biochemically recurrent PC following prostatectomy. Key inclusion criteria include histologic prostate adenocarcinoma, either Gleason 7 with T3/positive margin/1-4 positive lymph nodes or Gleason 8-10 disease, PSA relapse within 4 years of prostatectomy (minimum PSA 0.2 ng/mL to maximum PSA 4 ng/mL). Treatment involves ADT with apalutamide for 9 months, continue with with prostate bed +/- nodal RT at month 3, followed by 6 cycles of docetaxel 75mg/m2 IV every 3 weeks for 6 cycles. The primary endpoint of the study is 3-year PFS. With a one-sided alpha of 0.05 to improve 3-year PFS from 50% to 75%, we will have 92% power by enrolling 42 pts (including 10% dropout rate) based on the binomial test. Key secondary endpoints include 1, 2, and 3-year PSA recurrence rates with testosterone recovery, PSA PFS, PSA nadir, time to testosterone recovery, and safety of combination therapy. Quality of life will be assessed by EPIC questionnaire. As of February 2019, we have enrolled and treated 12 pts in this PCCTC trial. Accrual to the STARTAR trial is ongoing (NCT03311555). Clinical trial information: NCT03311555.