Etiology, pathogenesis, basic principles of treatment of squamous cell carcinoma of the oral mucosa

The review describes the current knowledge about the etiology and the main treatment methods of the oral squamous c ell c arc inoma (SCC). Up to 9 0% of the oral malignant neoplasms are presented by SCC of the muc ous membrane.
Squamous cell carcinoma of the oral cavity is a form of oral cancer with a poor prognosis and high mortality. The molecular pathogenesis of SCC is complex and results from a wide range of events that include interactions between genetic mutations and altered levels of transcripts, proteins, and metabolites. A reliable relationship has been established between a number of external and internal factors affecting the oral mucosa (OM) and the development of cancer. Precancerous conditions of the OM are directly related to the presence of dysplasia of the oral epithelium: chronic traumatization of the oral mucosa (decayed teeth and their roots, poorly manufactured prostheses); precancerous lesions (Bowen’s disease, verrucous leukoplakia, leukokeratosis); chronic infections involving the oral cavity (HIV, AIDS, human papillomaviruses, primarily HPV-16, and to a lesser extent, HPV-18 and other strains; herpes viruses, fungal diseases, etc.); biological carcinogens: bad habits (smoking / chewing mixtures, including tobacco, consumption of alcoholic beverages); industrial hazards. In periodontal diseases, inflammatory mediators contribute to the destruction of the soft and hard tissues of the mouth, activating osteoclasts, which promotes the invasion of tumor cells into adjacent tissues and can lead to malignant transformation and cancer. The  role of N-nitrosonornicotine, usually found in tobacco products, in the development of head and neck cancer has been proven. An interaction has been noted between genetic polymorphisms associated with alcohol metabolism and alcohol consumption and the risk of head and neck cancer. It has been shown that low socioeconomic status, old age, and improper lifestyle have a stronger association with poor survival of patients with oral squamous cell carcinoma than the occupational hazards. Numerous studies evaluating the contribution of chronic trauma in carcinogenesis have shown that, while persistent mechanical irritation causes a DNA damage accompanied by increased activity of poly-ADP-ribose polymerase, at the same time, inflammation leads to oxidative stress and is accompanied by the release of chemical mediators — cytokines, prostaglandins, and tumor necrosis factor. The
recognized standards of antitumor treatment of oral mucosa SCC include combined treatment or selective use of one of the treatment methods, such as surgery, chemotherapy, radiation therapy, concomitant therapy, targeted therapy. To date, there is still no single treatment design of choice, however, the treatment can be presented in an algorithm. It is very important to select the appropriate therapy method/regimen, as severe toxic side effects lead to significant pain, while the benefit in improving outcomes requires evaluation.
Key words: squamous cell carcinoma of the oral cavity, oral mucosa Conflicts of interest. The authors have no conflicts of interest to declare.
Funding. The study was funded by the Russian Federation President Grant for young scientists –Doctors of Sciences. MD-36.2020.7.