[-2]proenzyme prostate specific antigen for prostate cancer detection: a national cancer institute early detection research network validation study.
OBJECTIVE
This study evaluated the [-2]proenzyme prostate specific antigen serum marker using a blinded reference specimen set from 3 National Cancer Institute Early Detection Research Network centers from men with an indication for prostate biopsy.


METHODS
Serum was collected before biopsy from 123 men with no prior biopsy or prostate cancer history. Specimens (cancer cases 51%, noncancer controls 49%) were selected equally from the 3 sites, and analyzed for prostate specific antigen, free prostate specific antigen, [-2]proenzyme prostate specific antigen, benign prostate specific antigen and testosterone (Beckman Coulter ACCESS(R) analyzer).


RESULTS
There was no difference in total prostate specific antigen concentrations (noncancer 6.80 +/- 5.20 ng/ml, cancer 6.94 +/- 5.12 ng/ml) among the groups. Overall %[-2]proenzyme prostate specific antigen had the greatest area under the curve (AUC 0.69) followed by percent free prostate specific antigen (AUC 0.61). For %[-2]proenzyme prostate specific antigen maximal sensitivity was 60% and specificity was 70%. A logistic regression model combining prostate specific antigen, benign prostate specific antigen, percent free prostate specific antigen, %[-2]proenzyme prostate specific antigen, [-2]proenzyme prostate specific antigen/benign prostate specific antigen and testosterone had an AUC of 0.73. In the 2 to 10 ng/ml prostate specific antigen range %[-2]proenzyme prostate specific antigen and the model had the largest AUC (0.73). The AUC for percent free prostate specific antigen was 0.53. Specificities for %[-2]proenzyme prostate specific antigen, the logistic regression model and percent free prostate specific antigen at 90% sensitivity were 41%, 32% and 18%, and at 95% sensitivity were 31%, 26% and 16%, respectively.


CONCLUSIONS
%[-2]proenzyme prostate specific antigen was the best predictor of prostate cancer detection compared to percent free prostate specific antigen, particularly in the 2 to 10 ng/ml total prostate specific antigen range. These findings provide a rationale for broader validation studies to determine whether %[-2]proenzyme prostate specific antigen alone can replace other molecular prostate specific antigen assays (such as percent free prostate specific antigen) for improving the accuracy of prostate cancer early detection. These findings also support the usefulness of well characterized, carefully collected reference sets to evaluate new biomarkers.
Sokoll
Lori J
LJ
Departments of Pathology and Urology, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA. lsokoll@jhmi.edu
Wang
Yinghui
Y
Feng
Ziding
Z
Kagan
Jacob
J
Partin
Alan W
AW
Sanda
Martin G
MG
Thompson
Ian M
IM
Chan
Daniel W
DW
D000230:Adenocarcinoma / Q000097:blood* / Q000175:diagnosis*; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D014408:Biomarkers, Tumor / Q000097:blood*; D042241:Early Diagnosis; D004792:Enzyme Precursors / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D054547:National Cancer Institute (U.S.); D009367:Neoplasm Staging; D011379:Prognosis; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis*; D012372:ROC Curve; D012044:Regression Analysis; D012680:Sensitivity and Specificity; D014481:United States
D014408:Biomarkers, Tumor; D004792:Enzyme Precursors; D017430:Prostate-Specific Antigen