Histopathological comparison of the effects of hematoporphyrin derivative on two different murine tumors using computer-enhanced digital video fluorescence microscopy.

A comparison study of the effects of hematoporphyrin derivative (HPD) photoradiation therapy on two different mouse sarcoma tumor model systems (RIF-1 + EMT-6) was performed. Twenty-four h after i.v. administration of HPD, the responses to total laser light doses of 50-400 J/cm2 were evaluated by histological examination and the uptake and distribution of HPD using a computer enhanced digital video fluorescence microscopy technique. In response to total laser light dose (630 nm) of 50-400 J/cm2, 40 mice with RIF-1 tumor showed only minimal superficial tumor necrosis upon histological examination and a 9-12% increase in maximal tissue fluorescence. In contrast, 40 mice with EMT-6 tumor showed marked areas of patchy coagulation necrosis and vascular hemorrhage at doses as low as 50 J/cm2 and essentially total tumor destruction at total light doses of 150 J/cm2 or more. A 59-74% increase in maximal tissue fluorescence was observed using digital video fluorescence microscopy. It is concluded that the greater efficacy of treatment in the EMT-6 tumor as compared to the RIF-1 tumor was due to the greater localization of HPD as demonstrated by digital video fluorescence microscopy.