Bouaoud J, Bossi P, Elkabets M et al. Unmet needs and perspectives in oral cancer prevention. Cancers (Basel) 2022; 14: 1815.

A network of research centres is needed to gather data.

Oral squamous cell carcinoma (OSCC) may be preceded by visible white (leukoplakia) or red (erythroplakia) lesions but many precancerous changes are not visible to the naked eye. If oral potentially malignant disorders (OPMD) can be identified, then earlier diagnosis and improved prognosis may be possible. While lesions may be associated with risk factors such as alcohol, smoking and betel nut chewing, many lesions occur in the absence of these. Visible OPMD can be monitored by biopsy (incision or excision) but there are challenges to define an OPMD classification system, to identify those OPDM at risk of malignant change and to develop prevention strategies which would manage bv oth visible and invisible OPMD.

Histopathology is the gold standard for diagnosing and grading OPMD. However, dysplastic changes are sometimes very subtle and may be overlooked. Immunohistochemistry may be a useful adjunct but standardised criteria of histological appearances are needed to overcome observer variability and improve reliability of diagnosis.

Biomarkers have been proposed to identify OPMD at risk of OSCC development. Loss of heterozygosity at various chromosomal sites have been validated but longer term studies are needed to identify markers which may be useful in clinical practice. The accumulation of genetic changes is the driving force of carcinogenesis and therefore these chromosomal alterations may be the best predictors of malignant transformation.

A field of cancerisation is defined as 'a group of cells with tumour associated somatic genetic alterations' and can reach up to 10 cm in diameter. Microscopic dysplastic changes may be present or they may be visible macroscopically as red or white patches. They develop by a process of mutation relating to carcinogen exposure and may be stimulated by environmental cues.

Areas where research is developing include the role of the immune system - OPMD may resemble 'self' and not trigger an immune response or that malignancy develops in the presence of an immunosuppressive microenvironment - and the role of the oral microbiome.

The early detection of OPMD serves the purpose of secondary prevention of oral cancer. Visual examination and palpation are the conventional methods. Various optical and imaging techniques have been shown to improve identification of OPMD compared to clinical examination but suffer from low specificity. The lack of agreed histopathological standards makes the development of predictive algorithms very difficult.

Primary prevention of OPMD - elimination of risk factors such as smoking - remain the first line of management. Regular biopsy and possible surgical resection may be needed. There is no evidence of useful medical intervention which will prevent malignant transformation of OPMD.