POSTOPERATIVE SERIAL PROSTATE-SPECIFIC ANTIGEN AND TRANSRECTAL ULTRASOUND FOR STAGING INCIDENTAL CARCINOMA OF THE PROSTATE

Objectives To examine the value of post-operative serum prostate-speci fic antigen (PSA). PSA density, incremental change in serial serum PSA (PSA slope) and transrectal ultrasound (TRUS) in the assessment of re sidual malignancy after the diagnosis of clinically unsuspected prosta tic adenocarcinoma at transurethral resection of the prostate (TURP). Patients and methods Forty-eight untreated patients with incidental ca rcinoma of the prostate, demonstrated at TURP for a clinically benign gland, were evaluated post-operatively with serum PSA and TRUS with mu ltiple systematic prostatic biopsies. Prostatic volume was determined from TRUS measurements and PSA density was defined as serum PSA divide d by gland volume. Those patients who did not undergo further treatmen t were monitored with serial PSA levels, and PSA slope was calculated as the overall annual percentage increase in serum PSA. Results Among 36 patients staged T1A (Al), 11 (31%) had histologically proven residu al carcinoma, and five of the 12 patients (42%) with T1B (A2) disease had no residual disease on biopsy. Serum PSA levels following TURF wer e greater in those patients with residual disease than those without ( P=0.001), but at a cutoff of 4.0 ng/mL - providing a sensitivity of 89 % the specificity of PSA alone was 57%. PSA density had an 83% sensiti vity and a 67% specificity with a cut-off of 0.15 ng/mL/cm(3). TRUS ha d a sensitivity of 63% and a specificity of 52%. An incremental rise i n PSA exceeding 20% per year in untreated patients gave a sensitivity of 90% and specificity of 79% for biopsy proven residual malignancy. C onclusion This study demonstrates the inaccuracy of staging incidental prostatic malignancy by TURF. Although the performance of PSA density is better than that of PSA alone, the reliability of both are limited by the lack of specificity, and TRUS imaging lacks both sensitivity a nd specificity. The PSA slope has sufficient sensitivity and specifici ty to distinguish reliably most patients with biopsy proven residual m alignancy. Although ultrasound-guided systematic biopsies provide a me ans for confirming residual malignancy, they may not be indicated in a ll patients with incidental carcinoma: for such patients, PSA progress ion may provide a rational basis for subsequent treatment.