LASER-INDUCED FLUORESCENCE DIAGNOSIS AND PHOTODYNAMIC THERAPY OF HUMAN RENAL-CELL CARCINOMA

Photodynamic therapy (PDT) has recently attracted mucht attention, esp ecially among urologists, because it appears to be a selective form of cancer treatment which causes minimal damage to normal surrounding ti ssues. In this study we made use of a new class of photosensitizers fo r the laser-induced fluorescence diagnosis (LIFD) and photodynamic the rapy of human renal cell carcinoma xenotransplanted into nude mice. Th e purpose of this study was to evaluate the recently developed photose nsitizing drug THOPP-MPEG for its efficacy as photosensitizer for LIFD and PDT of renal cell carcinoma. THOPP-MPEG was injected intraperiton eally (0.5 mu g/g body weight) into the mice 6-8 days after tumor tran splantation. On the 18th day after transplantation, the tumors reached a diameter of 3-4 mm. Seven days after administration of the drug the tumor-bearing kidney was irradiated percutaneously with a total light dose of 2 x 60 J/cm(2) and a power density in the irradiated area of less than 150 mW/cm(2). A continuous-beam argon-pumped dye laser (656 nm) was used. After excitation with laser light (488-514 nm), the vita l tumor clusters and the surrounding tissues invaded with tumor cells showed intense red coloration by laser-induced fluorescence. Subsequen t to the light exposure (656 nm),a heavy tumor necrosis of up to 3-5 m m resulted. No THOPP-MPEG phototoxicity in normal surrounding tissue a t a dose of up to 100 mg/kg body weight was seen. We believe the futur e role of PDT in the management of tumors of the kidney to be adjuvant within the concept of conservative kidney-preserving surgery.