Background: AA men have higher prostate cancer  PC  incidence and mortality than CAU men, potentially related to biologic or socioeconomic factors. A retrospective subgroup analysis suggested greater overall survival  OS  benefit in AA metastatic castration-resistant PC  mCRPC  pts treated ith sip-T compared ith the overall population  McLeod et al, AUA 2012, abstract 953 . Data on AA and CAU pts from PROCEED  NCT01306890 , a phase 4 registry of mCRPC pts receiving sip-T, may further delineate treatment benefit for AA men. Methods: Men age 18 y ith mCRPC treated ith sip-T ere enrolled in PROCEED. Baseline pt characteristics, treatment history, safety, OS, ACIs, and time to ACIs  tACI  ere recorded. Results: 902 pts received 1 sip-T infusion, including 231  11.7 percent  AA men. Primary Gleason score 5 as more common in CAU pts  plt0.05 . In AAs, median baseline prostate-specific antigen  PSA  as higher  plt0.001 , and PSA doubling time  PSADT; plt0.01  as shorter  Table . Other baseline pt characteristics ere similar beteen groups. A trend toard loer percentage of AAs receiving radical prostatectomy before sip-T  p=0.06  as observed. Postsip-T, both groups had similar time to first  CAU 7.3 vs AA 6.9 mo  and second  CAU 28.7 vs AA 27.1 mo  ACI. Over 30 percent of pts had not received an ACI 12 mo after sip-T  CAU 32.3 percent vs AA 31.9 percent . Conclusions: Despite higher baseline PSA in AA pts, hich may predict less clinical benefit postsip-T, CAU and AA pts had similar tACI after sip-T. Additional follo-up ill assess potential OS differences in AA and CAU pts. Clinical trial information: lta href=http:clinicaltrials.govshoNCT01306890 NCT01306890Characteristic, n   percent CAU n=1,711 or as noted AA n=231 or as noted Gleason sum--x2003;x2003;x2003;x2003;7516  30.2 67  29.0 x2003;x2003;x2003;x2003;8875  51.1 106  45.9 Primary Gleason score 5n=1478n=184208  14.1 x002A;17  9.2 x002A;Positive lymph nodes538  31.4 78  33.8 Bone metastasisn=1430n=191x2003;x2003;x2003;x2003;1-10997  69.7 136  71.2 x2003;x2003;x2003;x2003; 10248  17.3 29 15.2 ECOG PS--x2003;x2003;x2003;x2003;01130  66.0 141  61.0 x2003;x2003;x2003;x2003;1501  29.3 80  34.6 Alkaline phosphatasea, UL8187Lactate dehydrogenasea, UL185192Time from diagnosisa, mo59.472.0PSAa, ngmL13.9x2020;33.2x2020;PSADTa, mo8.36x002A;x002A;8.01x002A;x002A;ltfn id=TF-161972-001-1 ltp class=mtgabstract-table-fn aMedian. x002A;p=0.03; x2020;plt0.001; x002A;x002A;p=0.007 for CAU vs AA.lttable-rap-foot ,J Clin Oncol 34, 2016  suppl; abstr 5025 ,NCT01306890,00:00.0,Genitourinary  Prostate  Cancer