Thermal considerations in murine tumor killing using hematoporphyrin derivative phototherapy.

Tumor cell killing utilizing hematoporphyrin derivative (HPD) phototherapy was studied in a murine tumor model to assess the relative importance of intratumor temperature in causing the tumoricidal effect. Temperature measurements and tumor killing without HPD strongly suggest that HPD phototherapy as reported previously by other workers has at least partially a hyperthermic effect. Also, it is shown that, in this tumor model, tissue light attenuation restricts the radius of action of the light-HPD interaction to approximately 4 mm.