BACKGROUND. The objective of the current study was to determine the histologic and molecular changes that occurred in patients with high-risk, localized prostate cancer (PCa) after neoadjuvant docetaxel chemotherapy. METHODS. Patients who had locally advanced PCa (serum preoperative [initial] prostate-specific antigen [iPSA] level >15 ng/mL, or clinical >T2b disease, or biopsy Gleason score [GS] >8) and no evidence of metastatic disease received 6 doses of intravenous docetaxel (40 mg/m2) administered weekly for 6 weeks followed by radical prostatectomy (RP). The Wilcoxon signed-rank test was used to compare pretreatment and posttreatment markers. RESULTS. Twenty-eight patients completed chemotherapy and underwent RP at the Cleveland Clinic; none achieved a pathologic complete response. Pretreatment diagnostic prostate biopsies (PBx) were reviewed in all patients, and unstained sections of formalin-fixed tissue were available from 11 patients. The median patient age was 62 years (range, 49-72 years), and the median iPSA was 6.8 ng/mL (range, 2.5-24 ng/mL). At a median follow-up of 49.5 months (range, 23-72 months), 12 patients (43%) remained clinically and biochemically free of disease with no additional therapy, and 16 patients (57%) had biochemical failure. The pretreatment GS was 6 in 2 patients (7%), 7 in 10 patients (36%), 8 in 11 patients (39%) and 9 in 5 patients (18%). Two patients (7.1%) had organ-confined disease, and 23 patients (82.1%) had extraprostatic extension. Four patients (14.3%) had positive lymph nodes, and 11 patients (39.3%) had seminal vesicle involvement. Immunohistochemical (IHC) staining for a panel of markers involved in various cellular functions (α-methylacyl- coenzyme A racemase [AMACR], β-tubulin I, β-tubulin III, cyclin D1, p27, p21, Ki-67, p53, Bcl-2, and an apoptosis detection kit [ApopTag]) was performed on a tissue microarray that contained the posttreatment (RP) tissue specimens and on the PBx specimens, if available. When the IHC staining patterns were compared between PBx and RP specimens using the Wilcoxon signed-rank test, only p53 expression (P = .017) and Bcl-2 expression (P = .014) were found to be increased significantly after neoadjuvant docetaxel treatment. However, after performing the Bonferroni adjustment, these differences were no longer significant (P > .005). Ki-67, ApopTag, β-tubulin I, and β-tubulin III expression levels also were increased after treatment; however, the differences were not found to be statistically significant. The expression levels of AMACR, p27, p21, and cyclin D1 were comparable in pretreatment and posttreatment specimens. CONCLUSIONS. The current results indicated that, although it will require longer follow-up studies and larger numbers of patients to ascertain the value of neoadjuvant treatment, the negative findings of the current study may explain the lack of clinical response in patients who received neoadjuvant docetaxel for PCa. Although the results were subject to interpretation limits based on the study size, the increased expression of p53 and Bcl-2 that was detected after treatment using the Wilcoxon signed-rank test suggested that the apoptotic pathway may be an important target for this drug, and further investigation is warranted. © 2007 American Cancer Society.