Clinical and biologic factors for immune response to sipuleucel-T (SipT) for metastatic castrate-resistant prostate cancer (mCRPC).

219 Background: SipT prolongs overall survival of men with asymptomatic or minimally symptomatic mCRPC. Recently, it has been demonstrated that SipT immune parameters correlate with survival. We prospectively collected biological and inflammatory markers as part of an audit to identify possible predictors of immune response in patients (pts) receiving SipT. Methods: Circulating tumor cells (CTC), PSA, prostatic acid phosphatase (PAP), albumin (Alb), hemoglobin (Hb), serum alkaline phosphatase (SAP), LDH, C-reactive protein (CRP) and β2-microglobulin (β2m) were evaluated in reference lab before SipT. Product parameters CD54, CD54 upregulation (UPREG) and total nucleated cells (TNC) were measured by Dendreon. These datasets were analyzed using Spearman coefficients for continuous variables and the Kruskal-Wallis test for categorical variables. Results: 92 pts who received SipT were included. Median age was 69 (48-90). 43% had Gleason 8-9. 42% had ECOG Performance Status (PS) 0, 44% PS 1, and 13% PS 2. 26% h...