Effect modifier analysis. Forest plot for putatively prognostic factors. Continuous factors are analyzed by dichotomization at the common median. PROSTVAC, a vaccine containing two recombinant viral vectors (vaccinia and fowlpox) and three immune costimulatory molecules (B7.1, ICAM-1, and LFA3); HLA-A2, human leukocyte antigen A2; PSA, prostate-specific antigen; Alk phos, alkaline phosphatase; LDH, lactate dehydrogenase; HGB, hemoglobin; ECOG PS, Eastern Cooperative Oncology Group performance status.