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-specific antigen (PSA). PSA density, incremental change in serial serum PSA (PSA slope) and transrectal ultrasound (TRUS) in the assessment of residual malignancy after the diagnosis of clinically unsuspected prostatic adenocarcinoma at transurethral resection of the prostate (TURP). Patients and methods Forty-eight untreated patients with incidental carcinoma of the prostate, demonstrated at TURP for a clinically benign gland, were evaluated post-operatively with serum PSA and TRUS with multiple systematic prostatic biopsies. Prostatic volume was determined from TRUS measurements and PSA density was defined as serum PSA divided by gland volume. Those patients who did not undergo further treatment 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 residual carcinoma, and five of the 12 patients (42%) with T1B (A2) disease had no residual disease on biopsy. Serum PSA levels following TURF were 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% sensitivity and a 67% specificity with a cut-off of 0.15 ng/mL/cm(3). TRUS had a sensitivity of 63% and a specificity of 52%. An incremental rise in PSA exceeding 20% per year in untreated patients gave a sensitivity of 90% and specificity of 79% for biopsy proven residual malignancy. Conclusion 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 and specificity. The PSA slope has sufficient sensitivity and specificity to distinguish reliably most patients with biopsy proven residual malignancy. Although ultrasound-guided systematic biopsies provide a means for confirming residual malignancy, they may not be indicated in all patients with incidental carcinoma: for such patients, PSA progression may provide a rational basis for subsequent treatment.