Abstract
BACKGROUND
Docetaxel‐based chemotherapy (DBC) showed limited clinical efficacy for castration‐resistant prostate cancer (CRPC) patients. To explore cancer vaccine as a new treatment modality, we conducted a phase II study of personalized peptide vaccine (PPV) for DBC‐resistant CRPC patients.
METHODS
Twenty DBC‐resistant CRPC patients and 22 patients with no prior DBC, as a control, were treated with PPV using peptides chosen from 31 peptides in patients, respectively. Cytokines, inflammatory markers, and immune responses were measured as candidate biomarkers. DBC‐resistant CRPC patients without PPV was set as a historical control for evaluation of clinical benefit of PPV.
RESULTS
Median overall survival (OS) time from the first vaccination was 14.8 months or not reached in DBC‐resistant CRPC patients and patients with no prior DBC (log‐rank; P = 0.07), respectively. Median OS time from the first day of progression disease was 17.8 and 10.5 months in DBC‐resistant CRPC patients receiving PPV and those with no PPV (P = 0.1656), respectively. Elevated IL‐6 levels before vaccination was an unfavorable factor for OS of DBC‐resistant CRPC patients (P = 0.0161, hazard ratio (HR): 0.024, 95% CI:0.001–0.499) as well as all 42 patients with PPV(P = 0.0011, HR: 0.212, 95% CI:0.068–0.661) by multivariable analysis.
CONCLUSIONS
Further clinical study of PPV is recommended for DBC‐resistant CRPC patients, because of the safety and possible prolongation of MST. Control of elevated IL‐6 by combined therapy may provide much better clinical outcome. Prostate 72:834–845, 2012. © 2011 Wiley Periodicals, Inc.
