Predictors Of Radiologic Progression Free Survival (Rpfs) During Abiraterone Acetate (Aa) Treatment In A Randomized Phase Ii Study Of Aa Maintenance In Combination With Docetaxel (D) After Disease Progression To Aa In Metastatic Castration Resistant Prostate Cancer (Mcrpc): Abido-Sogug Trial.

e16536 Background: AA improves OS and rPFS in asymptomatic/minimally symptomatic mCRPC patients. D is currently one of the standard treatments after progression to AA. However, the value of maintaining AA along with D despite progression to AA has not been tested. ABIDO trial aims to evaluate efficacy and safety of AA + D maintenance after disease progression to first line AA in mCRPC. Clinicopathologic features associated with rPFS during first line AA are presented. Methods: ABIDO trial is a randomized, phase II, open-label study with two stages. In stage I pts receive AA (1000 mg + prednisone (P) 10 mg qd) until progressive disease. In the stage II pts will be randomized to receive three-weekly D 75 mg/m 2 plus P 10 mg/d with (arm A) or without (arm B) AA 1000 mg/d. Pts had no visceral metastases, ECOG PS 0-1, and adequate organ functions. Clinicopathological predictors for rPFS to first line AA were estimated using the Kaplan-Meier method and independent associations were evaluated using Cox regression models. Results: 143 pts were included. Analyzed variables were: median age was 70y, 60% of pts had ECOG 0, 84% bone metastases (18% > 4), 42% BPI score 2-3, 53% Gleason > = 8, 30% PSA > 80 ng/mL, 38% node involvement and 11% had at least one lymph node > = 3 cm; 53% of pts achieved 4 weeks PSA reduction > 50%.Median rPFS was 18 months. Univariate analysis identified as significant variables: PSA, BPI, Gleason, node involvement, 4 weeks PSA reduction > 50%, and total volume of lymph node metastasis. On multivariate analysis, BPI (0-1 vs 2-3) (hazard ratio [HR] 1.81; p = 0.039), Gleason ( < 8 vs > = 8) (HR 2.51; p = 0.005), node involvement (no nodes, nodes < 3 cm and at least 1 node > = 3 cm (HR 2.8; p = 0.001 and 3.57; p = 0.009) and PSA reduction > 50% (HR 3.06; p < 0.001) were independently associated with rPFS. Median rPFS was superior in pts with 3 or more good prognostic factors (14m vs not reached; p < 0.001). Conclusions: BPI, Gleason, node involvement and 4-week PSA response were identified as independent prognostic factors for rPFS in first line AA treated patients. Clinical trial information: NCT02036060.