Proliferative Index Determination in Prostatic Carcinoma Tissue: Is There Any Additional Prognostic Value Greater Than That of Gleason Score, Ploidy and Pathological Stage?

Abstract

The proliferative index was evaluated as an additional prognostic variable in 244 radical prostatectomy specimens from patients with prostate cancer. This study was done on the grounds that this variable has shown some promise as a prognostic tool in some other carcinomas, for example breast cancer. The proliferative index was evaluated in 244 patients undergoing radical prostatectomy for clinically localized disease between January 1988 and August 1994. Proliferative index was determined using the Ki-67 antibody on fresh frozen tissue and MIB-1 on paraffin embedded tissues. Patients were divided into 2 groups based on a proliferative index of less than 1 (185) or 1 or greater (59). Of the patients 49 (20%) had biochemical failure (median 23 months to progressive prostate specific antigen elevation of 0.5 ng./ml. or more). Those whose treatment failed were also divided into 2 groups according to proliferative index: 32 of 185 (18%) with an index of less than 1 and 17 of 59 (27%) with an index of 1 or more. Gleason score and deoxyribonucleic acid ploidy status were also evaluated in all patients and compared in multivariate regression analysis. Operative specimens were categorized as organ confined, specimen confined or margin positive. The distribution according to margin status in the 2 groups (proliferative index less than 1 and 1 or more) was 40 versus 60% for organ confined, 67 versus 33% for specimen confined and 72 versus 28% for margin positive disease, respectively. The distribution of time to treatment failure in the 2 groups was not markedly different: 7.2 versus 9.4 months for margin positive, 10 versus 14.5 months for specimen confined and 8.5 versus 12 months for organ confined cancer, respectively. Multivariate analysis demonstrated that, although deoxyribonucleic acid ploidy seemed to correlate with more advanced disease, only Gleason sum and pathological T stage reached statistical significance when evaluated against time to treatment failure. A high proliferative index added little above the more traditional prognostic indicators of Gleason score, pathological stage and ploidy. Therefore, we question the value of proliferative index as a prognostic indicator using the aforementioned methodology in prostate cancer.