Abstract
BackgroundOral squamous cell carcinoma could be preceded by clinically evident oral potentially malignant disorders (OPMDs). Transformation of OPMDs to cancer has been studied in several population groups. It is difficult to undertake comparisons across populations due to variations in the methods of computation of malignancy rates among different studies. The aim of our study was to estimate the rate of malignant transformation of OPMDs taking into account the duration of follow-up and to identify the significant factors indicative of malignant potential.MethodsA total of 148 male patients with OPMDs were included. They were selected among all consecutive subjects registered at the maxillofacial clinic at a medical hospital in Kaohsiung, Taiwan. The mean follow up period was 37.8 months.ResultsThe malignant transformation rate was highest in subjects diagnosed with oral epithelial dysplasia. In this group the transformation rate was 7.62 per 100 persons-year. The rate in the group with verrucous hyperplasia (VH) was 5.21 per 100 persons-year, and in those with hyperkeratosis or epithelial hyperplasia was 3.26 per 100 persons-year. The anatomical site of OPMDs was the only statistically significant variable associated with malignancy. The hazard rate ratio (HRR) was 2.41 times for tongue lesions when compared with buccal lesions.ConclusionThe reported discrepancies of malignant transformation of OPMDs involve the follow-up time to cancer development and hence it is preferable to use a time-to-event estimation for comparisons. We found that malignant transformation of OPMDs involving the tongue was significantly higher than in other anatomical subsites after adjusting for the clinicopathological type or lifestyle factors at diagnosis.
Highlights
Oral squamous cell carcinoma could be preceded by clinically evident oral potentially malignant disorders (OPMDs)
The malignant transformation rates of OPMDs show a great variation; for example, 10–20% of hyperkeratosis or epithelial hyperplasia, epithelial dysplasia may transform to cancer and the estimated annual rate is 1.4%–7% [5,6,12,17]
In the US, 85% of OPMDs are hyperkeratosis or epithelial hyperplasia, epithelial dysplasia, and more than two thirds of all oral hyperkeratosis or epithelial hyperplasia, epithelial dysplasia are found on the lip, buccal mucosa and gingiva
Summary
Oral squamous cell carcinoma could be preceded by clinically evident oral potentially malignant disorders (OPMDs). The aim of our study was to estimate the rate of malignant transformation of OPMDs taking into account the duration of follow-up and to identify the significant factors indicative of malignant potential. The OPMDs include hyperkeratosis or epithelial hyperplasia, epithelial dysplasia [46], erythroplakia [7] and oral submucous fibrosis (OSF) [8,9] and their clinical phenotypes are well documented. Hyperkeratosis or epithelial hyperplasia, epithelial dysplasia and OSF are the most common oral mucosal disorders in the regions where areca quid chewing is prevalent, such as India, Taiwan, and other Southeast Asian countries [915]. The malignant transformation rates of OPMDs show a great variation; for example, 10–20% of hyperkeratosis or epithelial hyperplasia, epithelial dysplasia may transform to cancer and the estimated annual rate is 1.4%–7% [5,6,12,17]. In a recent study in Taiwan [19], the malignant transformation rate of OPMDs was estimated at 3.02% in an average follow-up period of 42.6 months, and the transformation rate ranged from 1.9 to 5.4% for various types of OPMDs
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