Photodynamic therapy of prostate cancer: an in vitro study.

The photo-induced toxicity of hematoporphyrin derivative on Dunning R3327 rat prostate cancer cells was studied. Dunning R3327 cells in culture were incubated for two hours in hematoporphyrin derivative and then exposed to red light at 630 nanometers wavelength from an argon pumped dye laser. Cell survival was measured for varying laser power densities, variable concentrations of hematoporphyrin derivative and variable light exposure times. AT1 cells not incubated with hematoporphyrin derivative were directly killed by laser light exposure at power densities greater than 500 mw./cm.2, probably due to hyperthermia. Cells that retained hematoporphyrin derivative were effectively killed using non-thermal levels of red light exposure due to a photochemical effect. Decreasing cell survival of cells that retained hematoporphyrin was related to increasing time of exposure to red light. This form of therapy may be applicable to the treatment of locally invasive prostatic carcinoma in man.