ABSTRACT
Prostate cancer (PCa) has traditionally been regarded as a multifocal disease, yet radical prostatectomy specimens have shown that 20%-30% of men with PCa may have unilateral or unifocal cancer. The concept of an index cancer was recently introduced to describe the largest cancer within a prostate, almost always the highest-grade cancer present, and the one likely to penetrate the capsule. The focus is on mapping the prostate in clinical scenarios where the prostate cancer is on surveillance protocol or on an active focal therapy treatment regimen. Therapeutic dilemmas leading to a decision to perform transperineal biopsy of the prostate may be encountered in two patient populations: active surveillance candidates and focal therapy candidates. Patients meeting criteria for active surveillance have minimal low-grade cancer on transrectal ultrasound-guided prostate biopsy. The concept of focal therapy has been criticized on the basis that prostate cancer is frequently multifocal.
