Combined abiraterone acetate plus prednisone, salvage prostate bed radiotherapy and LH-RH agonists (CARLHA-GEP12) in biochemically-relapsing prostate cancer patients following prostatectomy: A phase I study of the GETUG/GEP.

Background: To establish the maximum tolerated dose of abiraterone acetate plus prednisone (AA) combined with salvage radiotherapy (SRT) and goserelin in a phase 1 study in men with rising PSA following radical prostatectomy.

Methods: AA was given during one month before SRT at 1000 mg PO once daily, then 750 mg (Dose Level 1, DL1) or 1000 mg (DL2) during 5 months combined with 6-months goserelin by injection on the first day of irradiation (scheme NEO) or one month before starting SRT (scheme CONCO).

Results: In scheme NEO at DL1, 2/9 patients did not achieve castration levels of testosterone. 4/9 patients (44%) presented with grade 3 liver enzyme elevation. In scheme CONCO testosterone dropped to undetectable levels. At DL1, 6 patients were recruited, with no dose limiting toxicities. At DL2, 2/3 patients presented with grade 3 liver enzyme elevation occurring during SRT.

Conclusions: When AA was administered without goserilin, only 78% achieved castration levels. AA combined with SRT and goserilin did not increase pelvic toxicity, but lead to an unsuspected high frequency of grade 3 liver toxicity. The phase II recommended dose of AA combined to goserelin and SRT is 750 mg.