87 Background: TITAN showed that APA + androgen deprivation therapy (ADT) improves radiographic progression-free survival (rPFS) and overall survival (OS) in a broad group of pts with mCSPC (Chi et al. NEJM 2019). This post hoc analysis evaluates APA + ADT based on baseline (BL) prognostic risk as defined in LATITUDE (Fizazi et al. Lancet Oncol 2019). Methods: 1052 pts with mCSPC receiving ADT were randomized 1:1 to APA (240 mg/d; n = 525) or placebo (PBO; n = 527). Treatment cycles were 28 days. Risk included Gleason score ≥ 8, ≥ 3 bone lesions, or visceral metastasis. High risk was ≥ 2 risk factors, low risk was ≤ 1. Cox proportional hazards model was used to estimate HR and 95% CI for rPFS and OS. Results: Pt demographic and BL disease characteristics were similar between treatment groups (high risk: APA n = 289, PBO n = 286; low risk: APA n = 236, PBO n = 241). Median treatment duration was similar in the low-risk group with APA or PBO (21.8 mo and 20.3 mo, respectively). For the high-risk groups, treatment duration was longer with APA (APA 19.5 mo, PBO 14.7 mo). APA significantly reduced the risk of radiographic progression relative to PBO in both groups (Table). Risk of death (OS) was reduced by 38% in high-risk pts and 26% in low-risk pts with APA (Table). 24-mo survival rates: high risk, 76% APA, 63% PBO; low risk, 90% APA, 85% PBO. There were few deaths (≤ 33) in low-risk groups. Second PFS in APA pts: high risk, HR 1.9 (95% CI 1.2-3.0), p = 0.004; low risk, HR 2.2 (95% CI 1.5-3.2), p < 0.0001. Regardless of risk category, the safety profile of APA remained consistent with previously reported overall results. Conclusions: Addition of APA to ADT for pts with mCSPC prolonged rPFS and OS with a consistent safety profile compared with PBO + ADT regardless of BL risk. Clinical trial information: NCT02489318. [Table: see text]