The predictors of pelvic lymph node metastasis at radical retropubic prostatectomy

Purpose: We studied preoperative variables in a contemporary series of patients who underwent radical retropubic prostatectomy (RRP) to determine which variables were associated with lymph node metastasis. Materials and Methods: Between January 1995 and November 1999, 1,091 men underwent RRP, 695 of whom underwent bilateral pelvic lymph node dissection without any prior therapy. We evaluated biopsy Gleason score, maximum tumor length and maximum percentage of tumor in the positive core(s), location and number of positive cores, and total prostate specific antigen before surgery in 295 of these patients. We also developed a classification and regression tree analysis algorithm to segregate the risk of positive lymph node metastasis. Stepwise logistic regression analyses were used to determine independent predictors of lymph node metastasis. Results: Of the 695 patients 19 (2.7%) had lymph node metastasis. Clinical stage, Gleason score, positive basal core, greatest percentage of tumor on positive cores and maximum tumor length in positive core were significant predictors of lymph node metastasis in the Mann-Whitney U test and chi-square test. Classification and regression trees analysis revealed that 4 or more positive cores with any Gleason grade 4 or 5, serum prostate specific antigen 15.0 ng/ml or greater, or the presence of dominant Gleason 4 or 5 were independent predictors of lymph node metastasis. Our algorithm had a significantly higher diagnostic performance than the Hamburg algorithm (p = 0.002). Conclusions: Our algorithm may be a valid tool for the prediction of lymph node metastasis and may help to select men who do not need to undergo bilateral pelvic lymph node dissection with RRP.