Reply by Authors

PREDICTIVE VALUE OF PCA3 SCORE BEFORE PROSTATECTOMY 1979

tic determination using the full range of PCA3 scores as acontinuous value would be much more useful.

Yves FradetDepartment of Surgery

Laval UniversityQuébec City, Québec

Canada

PCA3 gene expression separates benign prostate from CaPwith an accuracy approaching 100% at the tissue level.1 Thegross over expression of PCA3 by cancer cells is the basis fora urinary CaP test to quantify the amplified gene in urinesamples (references 12 and 16 in article). In an era when thelimitations of PSA testing are increasingly apparent, thespecificity of the PCA3 gene for CaP cancer has createdconsiderable interest.

In this latest addition to the PCA3 story these authorsperformed the test in 72 men with CaP before radical pros-tatectomy. The PCA3 score correlated with final tumor vol-ume (r � 0.38, p �0.01) and it was also an independentpredictor of ECE. Independently a PCA3 score of greaterthan 47 predicted ECE with 94% specificity and 80% positivepredictive value. Remarkably when the PCA3 score wascombined with preoperative PSA and biopsy Gleason score,the ROC AUC for predicting ECE was approximately 90%.Thus, PCA3 expression appears to function synergisticallywith other clinical information.

However, the current data raise questions about PCA3.What is normal and what is abnormal? To date a PCA3 scoreof 35 has been considered the optimal cutoff but these patho-logical data, which were obtained without regard to thePCA3 level, suggest otherwise. The median PCA3 score inmen undergoing radical prostatectomy was 25, ie half of thepatients had a score below that level. Do these low scoresequate to falsely negative tests or do men with a low scorehave insignificant cancer, as suggested by Nakanishi et al

viewed in terms of positive or negative, but rather as agradation of risk. What regulates this peculiar noncodingstretch of mRNA? How should PCA3 scores be integratedwith other information, especially other molecular markers,to make treatment decisions? A lot remains to be learnedabout testing with this promising new marker, which at thetissue level is almost completely specific for CaP.

Leonard S. MarksUrological Sciences Research Foundation

Department of UrologyGeffen School of Medicine

University of California- Los AngelesLos Angeles, California

1. Schalken JA, Hessels D and Verhaegh G: New targets for ther-apy in prostate cancer: differential display code 3(DD3(PCA3)), a highly prostate cancer-specific gene. Urology2003; 62: 34.American Urological Association

REPLY BY AUTHORS

We highlight a promising prognostic use of the urine PCA3assay. Marks points out an important issue with respect torelatively lower PCA3 scores in a significant fraction of ourpatients with prostate cancer. We also are intrigued by thisobservation, and at this time it is unclear whether it is dueto our patient cohort, tumor biology or other technical is-sues. However, we did identify some uniqueness in our studypopulation such as a higher percentage of black men and thefact that men on active duty are screened at age 40 years.Marks makes a salient observation when he suggests that“Perhaps PCA3 scores should not be viewed in terms ofpositive or negative, but rather as a gradation of risk.” Thisconcept of PCA3 score as a continous variable was alsomentioned by Fradet. We look forward to future studies ofPCA3 in different cohorts and collaboration with other in-vestigators to further elucidate the usefulness of this latest