Background: AA men often present with more aggressive prostate cancer and are less likely to receive treatment, negatively affecting quality-of-life and overall survival (OS). Sipuleucel-T is an autologous cellular immunotherapy approved for asymptomatic or minimally symptomatic mCRPC. Data from the PROCEED registry showed that OS for AA pts treated with SIP-T was 9.3 mo longer than OS for Caucasian pts. In a prior subgroup analysis of Phase III data, AA pts realized a 30.7-mo difference in OS with SIP-T vs. placebo (PBO). We calculated the NNTB to further interpret the OS benefit in AA pts. Methods: Data were pooled from 3 Phase III mCRPC SIP-T trials (D9901, D9902A, and IMPACT). The absolute risk reduction (ARR) is calculated from Kaplan-Meier estimates at 12-, 24-, and 36-mo for all SIP-T subjects, and an AA cohort, receiving ≥1 infusion. NNTB, the inverse of the ARR, represents the number of pts needed to be treated with SIP-T to prevent 1 additional death compared to PBO. All NNTB values are rounded up. Results: Of the 737 pooled mCRPC pts enrolled, 488 men were randomized to SIP-T (n=33 AA), and 249 to PBO. Baseline clinical characteristics between the SIP-T and PBO groups were well balanced; however, compared to overall SIP-T and PBO, AA SIP-T pts were more likely to have received prior chemotherapy, lower hemoglobin, and better performance status. The NNTB at 12-mo was the same (13) for both the pooled SIP-T and AA treated cohort. At 24-mo, the NNTB values were 10 for pooled and 5 for AA. At 36-mo, an NNTB of 8 (pooled) and 3 (AA) SIP-T treatments prevented 1 additional death (Table). Conclusions: This NNTB analysis shows a favorable survival benefit for AA men treated with SIP-T and all treated SIP-T subjects. NNTB values declined over 3-years, suggesting durability of clinical benefit with SIP-T, and that it may address a known survival disparity in AA with prostate cancer. Studies with larger sample sizes may confirm if AA pts derive a greater OS benefit from SIP-T. Clinical trial information: NCT00065442