Commentary

According to the World Cancer Research Fund (https://www.wcrf.org/dietandcancer/cancer-trends/worldwide-cancer-data) there were an estimated 354,864 new cases of lip and oral cavity cancer and 92,887 cases of oropharyngeal cancer in 2018, representing 2.6% of all cancers. Oral cavity and oropharyngeal cancers are commoner in men and there is marked geographical variation with the largest number of diagnosed cases seen in south-central Asia. Survival rates are low with late presentation being an important factor. Early diagnosis is seen as important in improving treatment and survival. A number of oral potentially malignant disorders (OPMD) precede the development of oral squamous cell carcinoma (OSCC), the most frequent malignant neoplasm of the oral cavity, the main ones being oral leukoplakia (OL), oral erythroplakia (OE), oral submucous fibrosis (OSMF), oral lichen planus (OLP) and actinic cheilitis (AC). The aim of this review was to estimate the global prevalence of these OPMDs.

The authors have conducted a broad search of a number of databases and taken the decision to focus only on those observational studies with a histological diagnosis. While a summary of the characteristics of the included studies is available as a supplement to the main article there is limited information on the study designs, as all are described as descriptive, and no indication as to whether they are pro- or retrospective. The decision to use only studies with a confirmed histological diagnosis means that the data are derived from a cohort of referred patients rather than a broader population-based sample; this is demonstrated by the fact that the risk of bias assessment noted that only two of the twenty-two included studies were representative of the overall target population. These points together with the fact that only three of the included studies were considered to have been at low risk of bias need to be taken into consideration when assessing the reviews findings.

The review found an overall prevalence of OPMD = 4.47% (95% CI; 2.43 - 7.08) that was more common in males [59.99% (95% CI 41.27 - 77.30). The overall prevalence of OPMDs ranged from 10.54% (95% CI; 4.60 - 18.55) in Asian populations to 0.11% (95% CI; 0.004 - 0.37) in North American populations (Table 1). Oral submucous fibrosis was the most prevalent of the lesions (4.96%) with non-homogeneous oral leukoplakia (0.16%) the least common (Table 2).

Table 1 Regional prevalence of oral potentially malignant disorders
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Table 2 Prevalence of potentially malignant disorders
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The regional references highlighted in the review are not unexpected and likely to be due in part to habits that increase risk such as the use of betel nut products which are commonly used in south Asia.

While the review provides a helpful estimation of the prevalence of OPMDs in a range of populations the limited quality of the available studies, in particular the fact that few of the included studies were representative of the overall target population, mean that these estimates should be viewed cautiously.