Impact of prostate cancer multifocality on its biology and treatment.

Any focal therapy requires correct localization of the lesion; consequently, much effort is now devoted to accurate characterization of the spatial distribution of the tumor within the prostate. One of the greatest difficulties in the localization of prostate cancer is its frequent multifocality, but prostate cancer is unifocal in 13% to 43.7% of cases and unilateral in 19.2%. In cases of multifocality, it seems that the index tumor is the biologic driving force behind the malignant potential of prostate cancer. Not only is the Gleason score of the secondary nodes lower than that of the index node, but 80% of the secondary nodes are smaller than 0.5 cc and almost all extraprostatic extensions are associated with the largest cancers. While current evaluation with 12 to 18 core biopsies may be adequate to determine the index lesion, transperineal three-dimensional mapping biopsy of the prostate should be undertaken if greater accuracy is needed.