Cancer localization by detection of fluorescence by means of HpD administration and krypton ion laser photoradiation in canine lung cancer

A laser photoradiation system for the localization of lung cancer by detection of fluorescence emitted by hematoporphyrin derivative (HpD) was tested in experimentally induced malignant tumors in dogs. Canine lung cancer was induced by means of repeated submucosal injections of 20-methylcholanthrene at the bifurcation of the right apical and cardiac lobe bronchi. Four dogs with squamous cell carcinoma were used in this experiment and 5 dogs (4 dogs with cancer and 1 normal dog) were used as controls. 2.5—5.0 mg/kg body weight of HpD was administered intravenously in each dog 48 hours prior ttf examination for fluorescence. HpD is known to be retained longer by malignant tissue than by normal tissue and to emit fluorescence when stimultated by violet light. A krypton ion laser was used as a violet light source to excite the HpD, and an image intensifier and fiberoptic bronchoscope were used to detect fluorescence from the tumors. The cancer focus showed positive fluorescence in all cases. On the contrary, the control group which did not receive HpD injection showed no fluorescence.