Laser photobiomodulation does not alter clinical and histological characteristics of 4-NQO-induced oral carcinomas and leukoplakia in mice

Abstract

Objective: This study evaluated the effect of laser photobiomodulation (PBM) on oral leukoplakia and squamous cell carcinomas (OSCC) in a model of oral carcinogenesis.

Materials and methods: Forty-one C57Bl/6 female mice were distributed in control group, 4-NQO group, Laser group 1.5 J and Laser group 9 J. Oral cancer was induced on the tongue by nitroquinoline oxide (4-NQO), diluted in the water for 16 weeks. In the 18th and 19th weeks, PBM with a diode laser, 0.028 cm² spot size, continuous emission mode, 660 nm wavelength was applied on the tongue of animals for seven sessions. Laser group 1.5 J received 30 mW power and 1.5 J energy. In the Laser group 9 J, 100 mW power, and 9 J energy were applied. In the 20th week the animals were euthanized.

Results: All animals exposed to carcinogen developed clinical and histological alterations such as leukoplakia and OSCC on the tongue. There was no significant difference among Laser groups 1.5 and 9 J and 4-NQO group (not irradiated) regarding the area of leukoplakia and carcinomas (P > 0.05) or thickness of epithelial tissue and keratin (P > 0.05). There were also no association between PBM and histologic classification of the lesions (P = 0.87), frequency of OSCC (P = 0.57), grade of tumor differentiation (P = 0.88) or depth of invasion (P = 0.45).

Conclusion: Laser PBM, in both parameters used, does not influence on clinical and histological characteristics of oral leukoplakia and OSCC.

Clinical relevance: Results suggest that PBM may be a safe treatment for adverse effects of antineoplastic therapies in patients with leukoplakia and OSCC.

Keywords: 4-NQO; Mice; Oral carcinogenesis; Photobiomodulation.