Background. The role of pathological response, which develops as a result of systemic therapy for localized and locally advanced high risk prostate cancer, is not still fully understood. There are no clear indications for neoadjuvant therapy and no data on the relationship between neoadjuvant therapy and median of overall or progression free survival. According to increasing interest for neoadjuvant chemohormonal therapy followed by radical prostatectomy, we evaluated the features of pathological response and its effects on overall and progression free survival rates.Objective. Estimating residual disease and pathologic response to neoadjuvant therapy of high risk prostate cancer and its relationship with oncological results.Materials and methods. This was a prospective randomized study: patients with prostate cancer of high and very high-risk groups (prostate specific antigen levels >20 ng/ml and/or Gleason score ≥8 and/or clinical stage ≥T2c) were treated with neoadjuvant chemohormonal therapy followed by radical prostatectomy (n = 36). The neoadjuvant course included the intravenous administration of docetaxel once every 21 days (75 mg/m2 up to 6 cycles) and the antagonist of the gonadotropin releasing hormone degarelix according to the standard scheme (6subcutaneous injections every 28 days). The prostate tissue was evaluated for the residual disease, features of pathological response according to the ABC system. Additionally, the expression of IHC markers (p53, bcl-2, p16, Ki-67, androgen receptors, c-MYC, ERG, PTEN) was evaluated on postoperative material using tissue microarray.Results. A totally of 480 H&Epostoperative and 775 H&E biopsy slides were analyzed. Group A included 10 (32.3 %) cases, group B — 16 (51.6 %), and group C — 5 (16.1 %). The variance analysis revealed a significant difference in the frequency of more localized forms of prostate cancer in group B (43.7 %) (p = 0.028). During assessment we did not found any relationship ABC system assignment and preoperative prostate specific antigen level, the presence of a positive surgical margin, the pathological stage of diseases or regional lymph nodes involvement. However, the values of relapse-free survival vary sharply between groups: the highest median of relapse-free survival was found in group B — 23.02 ± 12.61 months, patients of groups A/C could not achieve the level of median relapse-free survival — 11.7 ± 6.43 and 16.19 ± 16.54 months respectively.Conclusion. The effectiveness of neoadjuvant chemohormonal therapy for high risk prostate cancer can be assessed by the features of pathologic response through ABC system which has demonstrated own versatility and reproducibility in presented material. Neoadjuvant therapy with docetaxel and degarelix can improve the treatment outcomes of prostate cancer patients at high and very high risk of disease progression. The data on changes in the prostate tissue can be helpful in predicting the duration of the effect after chemohormonal therapy with subsequent surgery.