BPSA is a Potential Serum Marker for
Benign Prostatic Hyperplasia (BPH)

Leonard S Marks, Arlyn S Llanes, Los Angeles, CA, Harry J Linton, Carlton L Gasior, Lisa S Millar, Stephen D Mikolajczyk, Harry G Rittenhouse, William A Munroe, San Diego, CA, Lori J Sokoll, Alan W Partin, Daniel W Chan, Baltimore, MD.

Abstract to be presented at the 2001 AUA Meeting in Anaheim, CA on Wednesday, June 5, 2001.

INTRODUCTION AND OBJECTIVES: BPSA ("Benign-PSA") is an isoform of PSA that we have previously shown to be highly correlated with BPH nodules in the prostate transition zone. BPSA is present as uncomplexed, free PSA in serum. Recent antibody development has resulted in an improved serum BPSA immunoassay with high specificity and sensitivity, which has allowed for the quantification of BPSA. This is the first study to establish the range of BPSA levels in the serum of men with and without prostate disease.

MATERIALS AND METHODS: A dual monoclonal immunoassay with a minimum detectable concentration of 60 pg/ml BPSA and less than 1% crossreactivity to other forms of PSA was developed. Serum BPSA was measured in three new cohorts of men: 100 each with symptomatic BPH, biopsy-proven cancer prior to radical prostatectomy, and a control group of healthy, young men.

RESULTS: Men with BPH had a median total PSA of 2.7 ng/ml. BPSA ranged from 0 to 1.4 ng/ml (median 0.11 ng/ml). Men with biopsy-proven prostate cancer-but unknown volume of BPH tissue-had a median total PSA of 6.8 ng/ml, and a median BPSA of 0.11 ng/ml, indicating a relatively low proportion of BPSA to total PSA in the cancer group. Young men without prostate disease had a median of 0.6 ng/ml PSA and undetectable BPSA. The median percent free/total PSA for BPH and cancer was 21% and 11%, respectively, while the BPSA/total PSA had a median value of 3.5% and 1.6%, respectively. BPSA levels ranged from 0 to essentially 100% of the free PSA in individual patient samples, suggesting that BPSA represents a distinct sub-population of free PSA that may be associated with specific biochemical aspects of BPH.

CONCLUSION: We have developed a BPSA-specific assay and established that BPSA is absent in young men, but elevated in men with symptomatic BPH. While not specifically targeted as a prostate cancer marker, BPSA may also provide additional value in discriminating BPH from prostate cancer. BPSA is a BPH tissue-associated form of PSA that may represent an important new serum marker for the study, diagnosis and treatment of BPH.