Only unilateral treatment with WST11-medicated VTP will be performed during the study. Treatment will consist of a single, 10 minute, IV administration of WST11 at doses of 2mg/kg, 4 mg/kg or 6 mg/kg, followed by either light activation delivered through transperineal interstitial optical fibers for 20 minutes using 753 nm laser light at escalating fixed energy doses of 200 J/cm or 300 J/cm by escalating power at each energy to 167 mW/cm or 250 mW/cm respectively. A brachytherapy-like template is used for the placement of the transparent implant catheters which are positioned in the prostate under transrectal ultrasound image guidance. The illumination fiber(s) are then inserted into the implant catheters.