Relationship and significance of greatest percentage of tumor and perineural invasion on needle biopsy in prostatic adenocarcinoma

Serum prostate-specific antigen (PSA) levels and the biopsy Gleason sum are used along with clinical staging to predict prostatectomy pathology result s for men with localized prostate cancer. The additional predictive value o f perineural invasion (PNI) in pretreatment prostate needle biopsies for ev aluating tumor stage in this setting is controversial. The current study ev aluates the independent predictive value of PNI for tumor staging in a coho rt of 632 men who underwent radical retropubic prostatectomies for clinical ly localized adenocarcinoma of the prostate between the years 1994 and 1998 . None of these men received hormonal or radiation therapy before surgery. In addition to the Gleason sum, biopsy results contained detailed informati on regarding tumor burden: 1) total number of biopsy cores involved by aden ocarcinoma, 2) greatest percentage of any single biopsy involved by prostat e carcinoma (GPC), and 3) total percentage of cancer added over all cores ( TPC). The presence or absence of any PNI was recorded. Pretreatment factors were analyzed in a univariate and multivariate fashion to determine their predictive value using the TNM tumor stage (pT2 vs pT3) and the modified tu mor staging system, which includes surgical margin status (pT2 vs pT3 or po sitive surgical margin) as end points. Univariate analysis revealed a signi ficant association between pT3 disease and several preoperative factors inc luding age, Gleason sum, serum PSA, digital rectal examination, PNI, GPC, T PC, and the total number of positive cores (p <0.01). Multivariate analysis indicated that serum PSA, Gleason sum, age, and GPC contributed significan tly to predicting pT3 disease with odds ratios of 2.7 (95% CI, 1.7-4.3), 2. 3 (95% CI, 1.7-3.1), 1.7 (95% CI, 1.1-2.7), and 1.7 (95% CI, 1.4-2.1) respe ctively. PNI was significant in multi variate analysis only when GPC and TP C were not considered, due to a significant interaction between GPC and PNI (p <0.0001,Wilcoxon's rank sum test). These predictive factors showed a si milar relationship to adverse pathology when an alternative definition of a dverse pathology was used that included positive surgical margins (pT3 or a ny positive margin). In the interaction between GPC and PNI, GPC was more s ignificant than PNI in predicting pT3 disease. However, PNI added additiona l information when adverse pathology was defined more broadly as pT3 or any positive margin.