Time to second progression (PFS2) in patients (pts) from TITAN with metastatic castration-sensitive prostate cancer (mCSPC) by first subsequent therapy (hormonal vs. taxane).

Abstract

82 Background: TITAN, a phase 3, randomized, double-blind study of apalutamide (APA) vs placebo (PBO) added to androgen deprivation therapy (ADT), demonstrated significant improvement in radiographic progression-free survival and overall survival in a broad pt population with mCSPC who received APA (Chi KN et al. NEJM 2019). This post hoc analysis evaluates whether type of 1st life-prolonging subsequent therapy (hormonal vs taxane) has an effect on PFS2 benefit shown with APA + ADT. Methods: PFS2 (the time from randomization to disease progression on 1st subsequent therapy for prostate cancer or death, whichever occurs first) was evaluated for pts from TITAN based on 1st subsequent life-prolonging therapy (hormonal vs taxane) after study treatment. Analysis censored all other 1st subsequent systemic therapies after start of treatment. Results: 277 pts (APA, 87; PBO, 190) received subsequent systemic therapy for prostate cancer; 86 pts (APA, 24; PBO, 62) received hormonal therapy (abiraterone acetate + prednisone or enzalutamide) and 99 (APA, 30; PBO, 69) received taxane (docetaxel or cabazitaxel) as 1st subsequent therapy. Baseline demographic and disease characteristics were generally similar between groups. The taxane group had a higher proportion of pts with high volume and pts with > 10 bone metastases, and a lower proportion with prior docetaxel exposure when compared with the hormonal group. Median treatment duration with APA and PBO was 11.9 and 11.1 mos in the hormonal group and 11.0 and 11.3 mos in the taxane group. Regardless of subsequent therapy, PFS2 was significantly longer for APA vs PBO (HR 0.66 [95% CI 0.50-0.87], p = 0.0026). Pts in both groups who received APA had a significant reduction in risk of 2nd progression compared with PBO (hormonal: HR 0.68 [0.48-0.97], p = 0.0326; taxane: HR 0.67 [0.48-0.94], p = 0.0189; medians not reached). Safety analyses were not conducted; all pts had discontinued therapy, most due to disease progression. Conclusions: The addition of APA to ADT for treatment of mCSPC results in risk reduction of 2nd progression regardless of choice of hormonal or taxane as the 1st life-prolonging subsequent therapy. Clinical trial information: NCT02489318.