Purpose: We determine whether biochemical prostate specific antigen (PSA) failure can be accurately predicted from preoperative serum PSA combined with 6 morphological variables from radical retropubic prostatectomy specimens in men with peripheral zone cancers. The unexpected limitation imposed by preoperative serum PSA on biochemical failure led us to compare peripheral zone to transition zone cancers.
Materials and methods: A total of 326 peripheral zone and 46 transition zone cancers treated only with radical retropubic prostatectomy were followed for a minimum of 3 years (mean and median greater than 5). All prostates were sectioned at 3 mm. intervals and morphological variables were quantitated using the Stanford technique. Biochemical failure was defined as serum PSA 0.07 ng./ml. or greater and increasing. Multivariate logistic regression was used to identify variables with the most independent influence on biochemical failure and derive a clinical equation to predict failure in peripheral zone cancers. The validity of the predictive equation was assessed by out of sample validation and cross validation techniques. The 46 transition zone cancers were compared to the 326 peripheral zone cancers by Student's t and Wilcoxon tests.
Results: Of the peripheral zone failures 60% occurred in the first year after radical retropubic prostatectomy and 95% had occurred by the end of year 4. The highest preoperative serum PSA was 23 ng./ml. among the 181 men biochemically free of disease. Only 15.8% of 57 men with PSA greater than 15 ng./ml. were biochemically disease-free. For the 48 transition zone cancers cure rates were independent of serum PSA with 6 men having PSA greater than 50 ng./ml. Biochemical disease-free status was noted in 80% of transition zone compared to 56% of peripheral zone cancers (p = 0.0009). The most important variables predicting biochemical disease-free status for peripheral zone cancers were percent Gleason grade 4/5, cancer volume, serum PSA and prostate weight. Foci of vascular invasion, intraductal cancer and lymph nodes were less significant variables, and capsular penetration, positive surgical margins and seminal vesical invasion were insignificant. The multivariate logistic equation for predicting failure in peripheral zone cancers was highly accurate and requires only 2 to 3 minutes with a simple calculator.
Conclusions: Failure of radical retropubic prostatectomy to cure peripheral zone prostate cancer is highly predictable based on 6 morphological variables from the prostatectomy specimen and serum PSA. The level of serum PSA profoundly limits biochemical cure rates in peripheral zone cancers. Transition zone cancers have a high cure rate, despite high serum PSA and adverse morphological variables. Men with serum PSA greater than 15 and perhaps even greater than 10 ng./ml. have such a low cure rate for peripheral zone cancer that re-biopsy attempts appear indicated to prove a transition zone location or else therapy other than radical retropubic prostatectomy should be sought. Pathologists should indicate whether the primary (largest) cancer is in the peripheral or transition zone to prevent overoptimistic reports of cure with radical prostatectomy procedures, as 85% of all tumors are in the peripheral zone.