**6. Disease epidemiology in the world**

Oral cancer is a serious and growing problem in many countries. Epidemiological studies show that the incidence of oral cancer and its mortality varies in different parts of the world [49]. In Australia, more than 4,000 new cases of head and neck cancer (including lip cancer) are diagnosed each year. Over 600 of these cancers are oral cavity cancers. In developing countries, oral cancer is the sixth cancer among men and the tenth cancer in women. Worldwide, more than 400,000 new cases of oral cancer are diagnosed each year, two-thirds of which occur in Asian countries such as Sri Lanka, Indonesia, India, Pakistan and Bangladesh [50]. In these high-risk countries, oral cancer is the most common malignancy, accounting for over 25% of all new cases of cancer each year [51]. According to the International Agency for Research on Cancer, some countries in Asia and the Pacific had the top three rates of oral cancer in 2018 [52].
