The Value and Evaluability of the PCA3 Urine Assay in Prostate Carcinoma is Independent of the Tumor Localization

The prostate cancer gene 3 (PCA3) test is based on the analysis of tumor cell mRNA in urine. As an exprimated urinary marker, its retrieval is subject to certain physical aspects like palpation pressure and detachment force during the squeezing of cells. Other potential factor of influence may be the distance the cells have to cover until they reach the urethra. Thus, it was investigated whether the localization of the tumors within the prostate with regard to the urethra and the seminal colliculus influences the PCA3 score.

Prostatectomy specimens of 55 organ-confined prostate cancer patients were processed according to the Stanford protocol. For each prostatectomy specimen, a three-dimensional reconstruction including the surface of the prostate, the tumor areas and the urethra was created. By model simulating, virtual concentric tubes were placed around the urethra and spherical volumes were virtually positioned around the seminal colliculus at diameters of 8, 16 and 32 mm. Depending on localization, tumor volumes may or may not protrude into the tubes or spherical volumes. For each respective diameter, PCA3 levels were compared between the subgroup with and without protrusion of tumor tissue into the tube or spherical ball.

For none of the diameters, whether in tubes or spherical balls, were patients without intersection volumes-hence showing peripherally located tumors-found to have lower PCA3 levels. No clinical or histopathological parameter correlated with the PCA3 score.

The location of the tumor mass in the prostate with respect to the urethra or the seminal colliculus did not to affect the PCA3 score. Hence, the location of the tumor does not limit the validity of the PCA3 score, and even for exclusively peripherall y located tumors, this possible influencing factor did not lead to an artificial modulation of the PCA3 score.