ALA/PpIX photodiagnosis of stress-induced gastrointestinal primary tumors and metastases in experimental animals

Gastrointestinal cancerous lesions were induced in laboratorial animals using prolonged exposure to social (overpopulation) and chemical stress (nitrosamine diet), mimicking typical stress factors for humans in the big cities. Twenty laboratorial rats with developed stress-induced neoplasia in gastrointestinal tract were used. Three of them formed control group - without application of exogenous contrast fluorescent marker. Exogenous fluorescent spectroscopic measurements were used to evaluate gastrointestinal tract (GIT) neoplasia development noninvasively using excitation at 405 nm and emission was detected in the region of 500-850 nm using microspectrometer. We used as exogenous fluorescent marker protoporphyrin IX applying its precursor delta aminolevulinic acid in a dose of 20mg/kg, in laboratorial rats with stress-induced neoplasia. Spectroscopic analysis of primary gastric tumours and their metastases spreading in rats' liver was carried out on animals in vivo, as excitation and emission light were delivered by fiberoptic probe 6+1 to the organs investigated during open surgery procedure. Biochemical indicators detected malignant alterations presence in GIT were also evaluated and used as complementary indices for lesions' growth. Fluorescent observation using exogenous fluorophore addressed the exact area and borders of neoplastic lesions in stomach and liver. In some cases in inflammatory areas significant accumulation of delta-ALA had place, which lead to false-positive fluorescent signal of protoporphyrin IX in these tissues. Photodiagnostics accuracy of 93% was reached for cancerous cases and 87% for gastric pre-cancer lesions evaluation. Very good correlation between fluorescence data and histology examination of the lesions investigated was achieved as well.