Treatment of mouse carcinomas with intratumoral injections of hematoporphyrin derivative and red light.

Hairless mice with subcutaneously transplanted Lewis Lung carcinomas were used to study the effects of treatments with hematoporphyrin derivative (HPD) administered by intratumoral injection, followed by exposure to red light. A tumor cure rate of 70-90% was obtained following a single treatment. The therapeutic response increased with increasing HPD doses and light fluences. At a certain dose a plateau seemed to be reached, where further dose increase only gave a limited gain in treatment response. A narrow range seems to exist between beginning therapeutic response and frank necrotic destruction. The number of mice that died after treatment increased with increase in tumor size, and there was a correspondence between the time of death and the severity of the phototoxic reactions. The best therapeutic response was obtained when the irradiation was performed 1/2-1 h after injection, and with tumors less than 6-8 mm in diameter.