Prediction of post-radical prostatectomy pathological outcome for stage T1c prostate cancer with percent free prostate specific antigen: A prospective multicenter clinical trial

Purpose: Prostate specific antigen (PSA) exists in bound (complexed) and un bound (free) forms in serum. The percentage-of free PSA enhances the specif icity of PSA testing for prostate cancer detection. We evaluated the use of percent free PSA preoperatively to predict pathological stage. Materials and Methods: A total of 379 men with prostate cancer and 394 with benign prostatic disease 50 to 75 years old were enrolled in this prospect ive study at 7 medical centers. All subjects had a palpably benign prostate gland, serum PSA 4.0 to 10.0 ng./ml, and a histologically confirmed diagno sis. The Hybritech Tandem PSA and free PSA assays were used. Of the 379 can cer patients 268 (71%) underwent radical prostatectomy. Results: Higher percent free PSA levels were associated with more favorable histopathological findings in prostatectomy specimens. A value of 15% free PSA provided the greatest discrimination in predicting favorable pathologi cal outcome. Organ confined cancer, Gleason sum less than 7 and small tumor s (10% or less involvement of the prostate) were noted in 75% of patients w ith greater than 15% and only 34% with 15% or less free PSA (p <0.001). Mul tivariate logistic regression analysis revealed percent free PSA to be the strongest predictor of postoperative pathological outcome (odds ratio 2.25) , followed by biopsy Gleason sum (2.06) and patient age (1.35). Total PSA w as not predictive in this cohort but has been shown in prior studies to be predictive of outcome when a broader range of PSA values is evaluated. Conclusions: Percent free PSA may be used for risk assessment of the presen ce (diagnosis) and stage of prostate cancer in men with PSA between 4 and 1 0 ng./ml. Percent free PSA may be combined with PSA, digital rectal examina tion and biopsy findings to help predict postoperative pathological stage a nd grade, and may assist the patient and physician in making more informed treatment decisions.