ENHANCED EXPRESSION OF PROSTATE-SPECIFIC ANTIGEN IN THE TRANSITION ZONE OF THE PROSTATE - A CHARACTERIZATION FOLLOWING PROSTATECTOMY FOR BENIGN HYPERPLASIA

Objective: To determine whether the serum levels of total prostate-spe cific antigen (t-PSA), free PSA (f-PSA) and PSA complexed to ai-antich ymotrypsin (PSA-ACT) result from different expressions ill various pro static zones. Methods: In a series of 127 consecutive men undergoing t ransurethral resection of the prostate (TURP) for BPH between May 1995 and February 1996, t-PSA, f-PSA (ProStatus(TM), Wallac) and PSA-ACT w ere measured before and 3-4 months after surgery. Pre- and postoperati ve prostate volumes were measured by TRUS. Resected tissue was assumed to be the transition zone (TZ) while postoperative volume was defined as peripheral zone (including the central one) (CPZ). Pre- and postop erative serum PSA was related to pre- and postoperative volume and res ected tissue to the difference between pre- and postoperative serum PS A, respectively. The serum PSA per 1 g tissue was calculated. Group I consisted of 96 historically proven BPH with no signs of inflammation, group II of 19 BPH patients with transurethral catheters inserted som etime prior to surgery to relieve urinary retention, and group III of 12 patients with incidental carcinomas. Results: In patients undergoin g TURF without prior catheterization (group I) t-PSA (group I) decline d from median 3.43 to 0.96 ng/ml after TURF by 72%, even though the pr ostate volume did so only by 44%, whereas the ratio free-to-total (f/t ) PSA remained stable (median 24.9% pre- vs. 26.6% postoperatively). T he TZ expressed approximately 2.7-fold more t-PSA than the remaining C PZ: median 0.14 vs. 0.052 ng/ml/g, respectively, and as to f-PSA it di d so likewise: median 0.032 vs. 0.012 ng/ml/g, respectively. With tran surethral catheterization prior to surgery (group II) the t-PSA densit y within whole prostate increased 1.4-fold as compared to this density without such catheterization: from median 0.089 (group I) to 0.13 ng/ ml/g tissue, respectively (p < 0.007), and within the TZ alone 1.6-fol d elevation from median 0.14 to 0.23 ng/ml/g, respectively (p < 0.02) was observed. In incidental carcinoma (group III) a reduced ratio of f /t PSA of 11.7% in the TZ as compared to 22.1% in the CPZ (22.1%) was observed. Conclusions: In BPH both t-PSA and f-PSA are predominantly e xpressed within the TZ, which could help to improve the specificity of the PSA density in cancer detection by using the sum of the t-PSA den sities of the TZ and CPZ: (0.14 ng/ml/g x TZ) + (0.052 ngl ml/g x CPZ) . It is the first time that the supposed origin of the incidental carc inoma (from the TZ) is confirmed biochemically by a f/t PSA ratio excl usively reduced in the TZ but not in the CPZ. The post-TURF unchanged free-to-total ratio (26.6%) may be useful for the early detection of c ancer in patients followed up after TURF.