Total and transition zone prostate volume and age: how do they affect the utility of PSA-based diagnostic parameters for early prostate cancer detection?

OBJECTIVES

To define the role of total prostate (TP) volume, transition zone (TZ) volume, and age as determinants of the utility of prostate-specific antigen (PSA)-based diagnostic parameters for early detection of prostate cancer (PCa) in a prospective multicenter study.

METHODS

The study participants were 974 consecutive men with serum total PSA (tPSA) levels of 4 to 10 ng/mL who were referred for early PCa detection or lower urinary tract symptoms. All patients underwent prostate ultrasound examination and sextant biopsy with two additional TZ biopsies. In patients with negative initial biopsies, repeated biopsies were performed at 6 weeks. tPSA, the free/total PSA ratio (f/t PSA), PSA density of the TZ (PSA-TZ), PSA density (PSAD), and PSA velocity (PSAV) were determined and compared across TP volume strata of 30 cm3 or less and greater than 30 cm3, TZ volume strata of 20 cm3 or less and greater than 20 cm3, and various age groups to evaluate the need for volume and/or age-specific reference ranges.

RESULTS

PCa was found in 345 (35.4%) of 974 patients and benign prostatic tissue was found in 629 (64.6%) of 947 patients. Across TP volume strata, significantly higher values of tPSA (P <0.01), PSA-TZ, PSAD (P <0.001), and PSAV (P <0.05) and lower values of f/t PSA (P <0.001) were observed in patients with PCa than in those without PCa. Similar results were obtained with respect to TZ volume strata, except in the case of PSAV (P <0.05). tPSA, PSA-TZ, and PSAD were significantly higher (P <0.05) in patients with PCa than in those without PCa for all corresponding age ranges. In patients with PCa, f/t PSA was significantly lower (P <0.001) within the same age ranges. Within each group (PCa or benign), f/t PSA, PSAD, PSA-TZ, and PSAV values were unaffected by age strata. However, PSA parameters dependent on prostate volume (PSAD, PSA-TZ) were statistically lower (P <0.001) in prostates with a higher TP volume (greater than 30 cm3) and TZ volume (greater than 20 cm3); f/t PSA values were unaffected by TP and TZ volumes.

CONCLUSIONS

f/t PSA and PSA-TZ were the most powerful parameters to differentiate between benign prostatic tissue and PCa. f/t PSA was the sole parameter unaffected by age and prostate volume. We believe new volume-specific cutpoints, as presented in the current study, should be employed when using PSAD and PSA-TZ for the early detection of PCa.