Correlation between serum prostate specific antigen levels and the volume of the individual glandular zones of the human prostate.

To analyze the correlation between serum prostate specific antigen (PSA) levels and the volume of the individual glandular zones of the human prostate, we examined 31 cystoprostatectomy specimens as well as 13 radical prostatectomy specimens with a prostate cancer volume of 0.3 cc or less, no bladder cancer infiltrating the prostate, no granulomas or severe inflammation, as well as no patient history of radiation, transurethral resection of the prostate or hormonal treatment. The volumes of the peripheral zone, transition zone and central zone were separately determined by outlining the zonal boundaries during microscopic examination of all slides at each level of section. PSA was measured by the Yang polyclonal assay. In the univariant regression analysis the correlation coefficients among serum PSA and transition zone, peripheral zone and central zone volumes were 0.934, 0.546 and 0.368, respectively, strongly suggesting that most PSA leakage from the prostate into the serum comes from the transition zone. The regression of serum PSA and transition zone volumes leads to a prediction of approximately 0.261 ng./ml. PSA per gm. benign prostatic hyperplasia (BPH) plus an intercept of 0.878, a number in keeping with our 1987 estimates of 0.3 ng./ml./gm. BPH. The volumes of the 3 zones appeared to be independent variables. Transition zone volume showed the greatest variation because of BPH. The mean average ratio of peripheral zone volume to central zone volume was nearly 3:1. These data strongly support the concept of age-adjusted PSA levels, since most of the increase in size of the prostate with increasing patient age comes from the transition zone from which BPH develops.