Objective: To determine the relationship between prostatic adenoma volume and serum prostate-specific antigen (PSA) levels in patients with benign prostatic hyperplasia (BPH), and to compare the predicted change in serum PSA following prostatectomy with the actual change observed.
Methods: Transrectal ultrasound (TRUS) estimation of prostatic adenoma (transition zone) and total gland volumes were calculated in 96 patients prior to prostatectomy. BPH was confirmed histologically following transurethral prostatectomy (in 86) and open prostatectomy (in 10). Serum PSA was measured preoperatively in all patients and post-operatively in 87 patients.
Results: Correlation coefficients of 0.607 and 0.614 were observed between PSA and adenoma and total gland volumes, respectively. The geometric mean ratio of PSA to adenoma volume was 0.120 micrograms/L/cc with 95% CI (0.104, 0.139) and to total gland volume was 0.068 micrograms/L/cc with 95% CI (0.058, 0.078). TRUS-determined adenoma and total gland volumes correlated well (r = 0.915), as did TRUS-determined adenoma volume and resected weight (r = 0.878). The mean ratio of change in PSA to resected weight was -0.096 micrograms/L/g with 95% CI (-0.128, -0.064). Neither total gland volume nor operation type affected the relationship between change in serum PSA and resected weight.
Conclusions: The adenoma should be the main determinant of serum PSA levels in patients with BPH. TRUS adenoma volume measurement is therefore the most appropriate preoperative measure when one is interpreting elevated levels of serum PSA in men thought clinically to have BPH.