10. STATISTICAL CONSIDER ATIONS 10.1 Study Design and Sample Size This is a single -center, randomized, 2 -arm, open -label, prospective clinical trial evaluating the immunogenicity and safety of ADT used alone (arm A), or ADT given in sequence with low -dose cyclophosphamide and prostate GVAX (arm B) , each administered 3 weeks prior to radical prostatectomy in men with high -risk localized prostate cancer. The primary goal of this study is to quantify the extent of CD8+ T cell infiltration into the prostate gland from patients in the two treatment arms , and to compare the two arms. Our primary hypothe sis is that men on the combination arm receiving cyclophosphamide /GVAX in addition to ADT (arm B) will have a 100 % or Androgen suppression with prostate GVAX and cyclophosphamide J1265 Johns Hopkins University 49 of 68 J1265 PROT (Vers) 1.4 113012 greater CD8+ T cell infiltr ation of the prostate than will men receiving ADT alone (arm A) . A difference smaller than this in the primary endpoint would not be considered biologically meaningful. In the absence of any intervention prior to prostatectomy , we have previously determined that the mean staining percentage for CD8+ T cells in prostate tumor tissue is 0.42 % (standard deviation 0.36%) (Gurel , De Marzo and Drake , unpublished data). W e hypothesize that men on the control arm (arm A) would have similar CD8+ T cell staining percentages as those quoted above. In the combination arm ( arm B ), a biologically meaningful treatment effect would be achieved if prostatic CD8+ T cell response s were augmented by 100 % or more compared to arm A . Therefore, with 16 patients per arm, and assuming an 86% coefficient of variation for the average CD8 area/spot area ratios, a one -sided 0.05 α -level t -test of the logarithms of these ratios would have 82% power to detect a 2 -fold (100%) increase of CD8+ T cells in the degarelix plus cyclophosphamide/GVAX arm (arm B) compared to the degarelix alone arm (arm A) . The safety of ADT monotherapy and the combination of ADT with cyclophosphamide/ GVAX delivered before prostatic surgery is an important co -primary endp oint. We hypothesize that combining ADT with low -dose cyclophosphamide and prostate GVAX in the neoadjuvant setting will be feasible and safe. Patients will be replaced if they are removed from the study after signing the informed consent but before receiving the study drug (s).