Background: STAND (NCT01431391) assessed optimal sequencing of sip-T and ADT in men with BRPC at high risk of metastases after local therapy (i.e. prostate specific antigen doubling time [PSADT] < 12 mo). Methods: Men (n = 68) were randomized to sip-T then ADT (2 wks post infusion 3; Arm 1) or ADT (3 mo lead-in) then sip-T (Arm 2). Cellular and humoral immune responses, and clinical outcomes were analyzed. PSA recurrence was defined as ≥ 2 serial rises in PSA and an absolute PSA value of ≥ 0.2 ng/mL (prior radical prostatectomy) or ≥ 2.0 ng/mL (prior radiotherapy alone). PSADT post-ADT was analyzed. Time to next anticancer intervention (TTACI) was measured from first ADT to the day of the next systemic therapy. Rate of metastases at 24 mo was also investigated. Results: All men received 3 sip-T doses, and 96% received 12 mo ADT. Cellular and humoral responses to PA2024 increased following treatment vs baseline (BL) and were sustained at all post-sip-T timepoints through 24 mo (p < 0.05). PA2024-specific T cell proliferation responses were higher in Arm 1 vs Arm 2 (p<0.001). The number of PA2024 antibody (Ab) responders (post-BL Ab titer ≥ 25,600) was similar between arms. Sip-T-mediated antigen spread was observed in both arms vs BL and maintained through 24 mo (p < 0.001). No significant differences between arms were observed in clinical outcomes: median time to PSA recurrence (21.8 vs 22.6 mo, HR: 0.70, 95% CI: 0.39–1.28; p = 0.357), PSADT (2.54 vs 2.58 mo, p = 0.944), metastases at 24 mo (6/31 vs 3/26, p = 0.419), or TTACI (medians not reached, p = 0.199). However, across the entire cohort, PA2024 Ab responses correlated with longer time to PSA recurrence (p = 0.007). Adverse events occurring in >20% were hot flashes, fatigue, headache, and chills. Conclusions: In men with non-metastatic BRPC, sip-T + 12 mo ADT induced a robust immune response that persisted for 24 mo. Data suggest a greater anti-PA2024 T cell proliferative response in Arm 1 (sip-T then ADT). Induction of a PA2024 Ab response may correlate with longer time to PSA progression. Clinical trial information: NCT01431391