Objective: The aim of the present study was to examine the efficacy of the volume-adjusted prostate-specific antigen (PSA) density as a predictor of pathological stage. Among patients who underwent radical prostatectomy for clinically organ-confined prostate cancer, we selected patients with PSA levels of 4-10 ng/ml. In these patients with borderline PSA value extent of disease is most difficult to predict. Using the transition zone (TZ) volume instead of the total prostate volume, we compared the ability of PSA to predict the tumor extent.
Methods: From April 1992 to November 1996, we examined 61 consecutive patients who underwent radical prostatectomy. Their age ranged from 52 to 78 years. The PSA densities for the total prostate volume (PSAD) and for the TZ volume (PSAT) were calculated by transrectal ultrasound examinations. To compare the usefulness of PSA, PSAD, and PSAT, the area under the receiver-operator characteristic (ROC) curve was calculated for each parameter.
Results: The final pathological stage was pT2N0M0 in 34 patients, pT3N0M0 in 20 patients, and pT3N1M0 in 7 patients. Accordingly, 34 patients (55.7%) had organ-confined prostate cancer. In patients with capsular perforation, the areas under the ROC curve were 0.686 for PSA, 0.665 for PSAD, and 0.860 for PSAT, while in those with seminal vesicle invasion the respective values were 0.712, 0.703, and 0.882. Thus, PSAT was superior to PSA and PSAD in differentiating extracapsular disease.
Conclusion: PSAT provides superior preoperative prediction of extracapsular tumor invasion, which appears to be useful in treatment selection (e.g. total prostatectomy).