An analysis of 148 consecutive transition zone cancers: clinical and histological characteristics

To improve our understanding of transition zone cancer in terms of the diagnosis and biological behavior we examined all morphological and clinical variables in 148 consecutive cases of untreated transition zone cancer after radical retropubic prostatectomy. We matched 79 cases by total cancer volume to 79 of pure peripheral zone cancer with no secondary tumors.

Using the Stanford technique of prospective 3 mm. step sections we identified 175 of 996 men (18%) with untreated transition zone cancer after radical retropubic prostatectomy who had the largest cancer volume in the transition zone. We excluded 27 patients from study due to previous transurethral prostatic resection or incomplete data. Preoperative serum prostate specific antigen (PSA) was determined by the Tosoh AIA-600 PSA assay. Postoperatively a PSA of 0.07 ng./ml. and increasing represented biochemical failure when the assay was done in the ultrasensitive mode.

Of the 148 cases of transition zone cancer 80% had organ confined disease, 70% stage T1c impalpable disease, 63% a positive initial prostatic biopsy, 62% unilateral cancer in the transition zone, 52% a secondary tumor only in the peripheral zone, 61% serum PSA 10 ng./ml. or greater preoperatively, 36% cancer volume greater than 6 cc and 24% at least 50% Gleason grade 4/5 cancer. Only 20% of the tumors were located in the proximal third of the transition zone near the bladder. The number of secondary tumors in the transition zone ranged from 1 to 12 (median 3) and secondary tumor volume ranged from 0.01 to 4.8 cc (median 0.6). Mean distance plus or minus standard deviation from the posterior prostatic capsule to the posterior border of the transition zone cancer was 12. 0 +/- 7.6 mm. (median 12.3). While only 15% of patients had capsular penetration, 29% had anterior positive surgical margins, 2.7% seminal vesicle invasion and 3.4% lymph node metastasis. When 79 transition zone cancers were matched by volume with 79 peripheral zone cancers, there were no differences in percent Gleason grade 4/5, serum PSA or prostate weight, although differences in clinical stage T1c to T2c and organ confined cancer were highly significant (p <0.0001). Kaplan-Meier curves showed that at 5 years of followup 49.2% of the men with peripheral zone cancer had undetectable PSA compared with 71.5% of those with transition zone cancer (log rank test p = 0.0002).

Our report should make it easier to diagnose transition zone cancer. The 72% biochemical PSA cure rate is significantly higher than the 49% cure rate for peripheral zone cancer. Since cancer volume and percent Gleason grade 4/5 disease were the same in these 2 groups matched by cancer volume, the differences in behavior of peripheral and transition zone cancers must be sought at the molecular level unless anatomical location alone explains the differences in progression. Pathologists should differentiate transition from peripheral zone cancer when analyzing radical prostatectomy specimens.