Abstract
Abstract only 320 Background: Sip-T is an autologous cellular immunotherapy approved by the FDA for the treatment of asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer. PROCEED (NCT01306890) is a phase 4 registry evaluating men receiving sip-T therapy in the US. Patient characteristics and treatment trends were assessed from 2011 to 2013, when several agents with an overall survival benefit became commercially available. Methods: For patients enrolled from 2011 to 2013, baseline patient and disease characteristics at the first sip-T infusion, trends in prior therapy, and pre–sip-T baseline prostate-specific antigen (PSA) levels were examined year over year. Results: From 2011 to 2013, 1902 patients were enrolled and received ≥ 1 sip-T infusion: 2011, n = 145; 2012, n = 967; 2013, n = 790. During this time period, enrollment of African American men nearly doubled from 6.9% to 13.4%, and central venous catheter use to facilitate sip-T infusion decreased (from 53.8% to 44.1%). Median baseline lactate dehydrogenase (LDH) levels and the number of lymph node metastases also decreased as well as median baseline PSA values (17.8 ng/mL to 11.9 ng/mL [P = 0.002]). Prior use of first-generation anti-androgens (from 73.1% to 60.5%), ketoconazole (17.2% vs. 6.3%), and estrogen (4.8% vs. 1.6%) decreased along with prior docetaxel use (19.3% vs. 7.5%). In contrast, prior investigational use of abiraterone acetate (from 3.4% to 8.9%) and enzalutamide (1.4% vs. 3.2%) increased over time. Conclusions: Over the duration of PROCEED, the decrease in baseline PSA, lower LDH, fewer nodal metastases, and decline in prior docetaxel use suggest that sip-T is being used earlier in the course of metastatic castration-resistant disease. Moreover, second-line hormonal therapy use with agents that do not improve overall survival appears to be substituted by therapies that do. This decrease in second-line hormonal therapies during PROCEED could suggest a real-world preference for earlier sip-T use. Clinical trial information: NCT01306890.