STUDIES OF TIN ETHYL ETIOPURPURIN PHOTODYNAMIC THERAPY OF THE CANINE PROSTATE

Abstract

Previous studies have demonstrated the technical feasibility of destroying prostate tissue using photodynamic therapy for benign and malignant disease. A series of canine studies was performed to evaluate the systemic uptake and distribution of the photosensitizer tin ethyl etiopurpurin (SnET2) in the prostate and surrounding tissues, and determine the optimal combination of drug dose, light dose and time interval between drug and light administration using transurethral and transperineal interstitial light delivery. Adult male mongrel source dogs received intravenous bolus injections of 0.5 or 1.0 mg./kg. SnET2 in 4 studies. In the first study the concentration of SnET2 in the prostate and surrounding tissue was measured at various time points after dosing. In the second study a tissue dose response relationship of SnET2-PDT was studied after transperineal interstitial light application. The third and fourth studies evaluated the tissue effects of combined transurethral and transperineal interstitial light application on SnET2 sensitized prostates. Substantial amounts of SnET2 were measured in the prostate between 24 and 168 hours after infusion. Drug and light dose dependent prostatic tissue necrosis and volume reduction were documented in the dose response relationship study. The combination of transurethral and transperineal light resulted in the extensive destruction of glandular epithelium with minimal damage to surrounding structures. Average prostate volume decreased 52%. Transperineal interstitial light delivery with multiple diffusers resulted in substantial glandular destruction of the prostate. An average volume reduction of more than 60% was achieved. SnET2-PDT is a viable minimally invasive treatment modality for prostate tissue destruction.