Photodynamic Diagnosis and Therapy of Oral Neoplasia using Toluidine Blue

(1) OBJECTIVE: Long-term goal: the development of a photodynamic approach to early detection, diagnosis and eradication of oral dysplasia and malignancy. Optical techniques offer many advantages and may benefit patients greatly. Specific aim:to evaluate (A) photodynamic diagnosis and (B) photodynamic therapy in the hamster cheek pouch carcinogenesis model at specific grades of pathology using toluidine blue (TBO) and light at 633nm.(2) METHODS: DMBA carcinogenesis was applied to one cheek pouch in 45 hamsters for 4-12 weeks. After topical application of acetic acid and 0.5% TBO, cheek pouches were visualized using in vivo fluorescence imaging to map TBO fluorescence, then irradiated using 15-60 J/cm2 for 3-12 min. Hamsters (a) not treated with TBO, (b) treated with TBO but no laser and (c) treated with laser but no TBO, served as controls. After laser irradiation, animals were sacrificed and tissues underwent histopathological preparation. Using (a) TBO fluorescence and (b) histopathology, lesion presence was scored as yes/no and lesion delineation was mapped microscopically using a grid and IPLabTM software.

(3) RESULTS: Areas of pathology were clearly identified by TBO fluorescence (k=0.85-0.95 for presence depending on pathology; k=0.80-0.90 for delineation). Most effective photodestruction occurred at laser parameters >= 30J/cm2 and exposure durations >= 6 min. Maximal photodestruction with minimal thermal damage was observed at 30 J/cm2 after 9 min irradiation. Selective photodestruction was evidenced by intra-vascular thrombosis and neovascularization in the pathological tissues. Cellular thermal damage was evidenced by atypical cell membranes, vacuolization and loss of inter- and intracellular integrity.(4) CONCLUSION: Topical toluidine blue may be a useful tool for photodynamic diagnosis and therapy of neoplasia in the oral mucosa.

Supported by: CA TRDRP 14IT-0097, NIH (LAMMP) RR01192, DOE DE903-91ER 61227, NIH EB-00293 NCI91717, NSF BES-86924. Zila Pharmaceuticals, Phoenix AZ, NIH RR-01192, EB0002SS, EB002494 and AR47551