Fluorescence detection of premalignant, malignant and micrometastatic disease using hexylpyropheophorbide

We investigated the in vivo fluorescence detection of premalignant and malignant lesions in carcinogen-induced tumors of the hamster buccal cheek pouch and micrometastases in rat lymph nodes using hexylpyropheophorbide-a (HPPH) at 0.5 mg/kg and He-Ne laser-induced fluorescence photometry. Time course studies of HPPH in hamster tumor model showed maximal relative fluorescence readings at 48 hours after i.p. injection in each stage (dysplasia: 0.35, papilloma: 0.58, squamous cell carcinoma: 1.04). Squamous cell carcinoma showed significantly greater fluorescence than papillomas and dysplasias at all time points (p<0.01). Metastatic lymph nodes were significantly greater than normal lymph nodes at all time points (p<().01). Maximal fluorescence levels of normal lymph nodes were observed at 6 hours after i.v. injection. Metastatic lymph nodes still showed high fluorescence levels at 72 hours. Micrometastases showed fluorescence levels between the levels of metastatic and normal lymph nodes (normal: 0.40< micrometastasis: 0.62< metastasis: 0.75 at 48 hours after i.v. injection). The results demonstrated good correlation between fluorescence levels and histopathological developments at all time points, Therefore, HPPH may be a promising fluorophore for the detection of developing malignancies and occult disease.