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Key Words: Oral cancer, epidemiology, risk factors, prevention, policy, tobacco, alcohol, diet, HPV
Oral Cancer is a mammoth challenge in India and ranks among the top three types of Cancers in the country, thus due to her large population count is considered to be the “Epicentre of Oral Cancer Epidemic”. The World Health Organization (WHO) regards oral cancer as a major public health challenge. The burden it imposes, in terms of incidence, mortality, survival and the determinants of disease, as well as the inevitable stretching of limited health care resources, is not fully appreciated. Malignant neoplasms of the lip, oral cavity and oro-pharynx [International Classification of Diseases (ICD)-codes: C00–C14], excluding other pharyngeal sites (C11–C13), are often grouped together. They have common risk factors and, to some extent, behaviours.
These conditions represent the sixth most common type of cancer in the world. Annual estimated global incidences amount to around 275,000 cases of oral and 130,300 cases of pharyngeal cancers excluding cancers of the nasopharynx, two thirds of which occur in developing countries. This Article intends to define oral cancer as any malignant neoplasm occurring on the lips or within the mouth/oral cavity, including on the tongue (ICD-10 codes: C00–C06). Diseases of the oropharynx (C10), pyriform sinus (C12) and hypopharynx (C13) have some commonality in risk factors and behaviour also. 90–95% of all new cases of oral malignancy in populations are squamous cell carcinomas (SCC) arising from lining mucosa. Squamous cell carcinomas of the oro and hypopharynx are increasing. Many cases are related to the traditional risk factors of smoking and heavy alcohol consumption, and others to infection with human papillomavirus (HPV). In the Indian context, oral cancer itself is most common, and its aetiology is dominated by tobacco use, especially of smokeless tobacco, areca [betel] nut consumption and alcohol abuse, all of which frequently act in the presence of poor diet and poor dental health. This is a preventable disease.
High Burden of Oral Cancer in India Age-adjusted rates of oral cancer in India are high, which is, 20 per 100,000population and accounts for over 30% of all cancers in the country. India contributes the highest number of new cases because of its huge population. Over five people die from oral cancer every hour, every day in India and almost the same number die from cancer of the oro-pharynx and hypopharynx. Diagnosis at later stages results in low treatment outcomes and considerable costs to the patients whom typically cannot aﬀord this type of treatment. Rural areas in middle- and low-income groups also have inadequate access to trained providers and limited health services. As a result, delay has also been largely associated with advanced stages of oral cancer. Oral cancer (ICD-10 codes: C01–C06) accounts for almost 40% of total cancer deaths.
Case Definition of Oral Cancer Due to the heterogeneity of pathologies presented in oral cavity tumour research, as well as the intraoral cavity evaluation with respect to the sub-sites such as the oropharynx, the case. Definition for oral cancer has been further complicated. Due to this failure to specify and define oral cancer in peer-reviewed literature, meaningful comparisons for description and epidemiological purposes have proved to be a challenge. To minimise misclassification errors and for the purpose of this review, oral cancer is defined as the cancer of the lip, mouth, and tongue, to include the anatomic description of the oral cavity as reported in previous major population-based research reports .Survival Marked differences in survival have been noted among rural, semi-urban and small urban registries in India, whereas differences are small between the registries of the major cities where more developed and accessible health care services are available. Poor survival rates can also be attributed to the fact that half of the oral cancer cases in the nation are diagnosed at advanced stages (stages III and IV) because patient’s delay in seeking medical care and acceptance of treatment is low.
Management Strategies Multiple treatment options are available in many centres. These include surgery or radiotherapy alone, and surgery with radiotherapy, with or without adjunctive chemotherapy. All of these cause tremendous physical, emotional and psychosocial disruption, but significantly worse health-related quality of life is experienced by patients who require both surgery and radiotherapy. Although adjunctive chemotherapy can lengthen survival, it is associated with considerable toxicity and uniformly effective agents and regimes have yet to be identified.
1. Aetiology The causes of malignant transformation of the oral epithelium and the processes of invasion and metastasis are as complex as for any other anatomical site. Genetic predisposition plays a minor role expressed through polymorphisms in carcinogen-metabolising enzymes, the expression of oncogenes and onco suppressor genes, and DNA repair genes. There is increasing evidence of the importance of chronic inflammation, alterations in host immunity, metabolism and neo-angiogenesis, all of which may be triggered or enhanced by viruses, radiation, chemicals (notably from tobacco and alcoholic beverages), hormones, nutrients or physical irritants.
2. Oral potentially malignant disorders The majority of oral cancers arise from pre-existing longstanding lesions, now termed ‘oral potentially malignant disorders’ (OPMDs) in recognition of the fact that systemic, cellular and molecular change are much wider than any particular macroscopically visible oral lesion. In India, tobacco is the major aetiological agent, producing visible lesions of which so-called leukoplakia is the most common. This association has led to the aphorism ‘cancer is where tobacco is’. This knowledge explains the focus for the primary prevention of oral cancer on population-based strategies and on the early detection of OPMDs; habit intervention and follow-up are regarded as secondary prevention strategies conducted on an individual basis.
3. Major risk factors. Risk factors may vary for different cultural and socioeconomic groups. However, established risk factors for oral cancer in the Indian population include: tobacco in all its forms (smoked, chewed, used as oral snuff); the chewing of betel quid(pan/paan); the heavy consumption of alcohol, and the presence of an OPMD. Other contributory or predisposing factors include dietary deficiencies, particularly of vitamins A, C and E and iron, and viral infections, particularly by those HPVs of known high oncogenic potential.
4. Age distribution. Although oral cancer has traditionally been thought of as a disease mainly affecting people of older ages, a substantial proportion of cases arise in the third and fourth decades of life. Increasing incidence with age has generally been attributed to indiscriminate substance abuse, particularly of tobacco and tobacco-related products, over a considerable period of time, which allows multiple genetic damage to accrue.
5. Gender differences. Males are, overall, at higher risk. The highest incidence rates for oral cancer in the world are seen amongst some subpopulations of women in southern India, and in emigrant populations from this area. This reflects the practice of heavy pan chewing (piper betel leaf filled with sliced areca nut, lime, catechu and other spices chewed with or without tobacco), poor nutrition and poor oral hygien
6. Areca nut. Areca nut is the fourth most commonly used psychoactive substance in the world after caffeine, nicotine and alcohol. It contains arecoline and 3-(methylnitrosamino) propionitrile, and lime provides reactive oxygen radicals, each of which contribute to oral carcinogenesis.
7. Alcohol drinking The effects of smoking and alcohol consumption on the risk for oral cancer are strongly synergistic. Multiplicative interaction between the consumption of alcohol and tobacco products, respectively, was observed to induce a 24-fold increase in risk for oral cancer. A cohort study conducted in Kerala revealed that approximately 80% of alcohol-dependent patients smoke cigarettes.
8. Human papillomavirus Since the first report of an association of HPV with SCC in 1977, numerous studies have explored the evidence for HPV in the aetiology of oral cancer. The association is strongest for cancer of the tonsil and other parts of the oropharynx. Positivity for HPV, specifically carriage of the high-risk genotypes HPV16 and HPV18, has come to be associated with a specific subgroup of oropharyngeal SCCs that arise preferentially among individuals with no history of significant long term consumption of tobacco and alcohol and have a favourable outcome attributable to an increased sensitivity towards radiotherapy.
- Socioeconomic determinant: All over the world, oral cancer is more prevalent amongst people of low socioeconomic status, partly because tobacco use in any form is more common in these population groups and such patients do less well because they have less access to care. Isolated studies conducted in small townships in India have shown that level of education is closely related to awareness of oral cancer and its risk factors.
- Current interventions for oral cancer control in India : India has several world-leading cancer treatment centres and clinical services are available across the nation. Because of the high case load, exceptional experience and expertise exists in head and neck oncology in many places. Both access to these and the facilities available of both staff and equipment are highly variable. Effective prevention is necessary to stem the epidemic are admirable and will, it is hoped, be rolled out across the entire country in due course. Synergising these with the activities of all other stakeholders will be important.
- Primary prevention: Primary prevention achieved by the modification of risk factors is the most cost-effective approach. The highest priority should be given to tobacco control. Special attention should be directed towards controlling the use of smokeless tobacco, which is rapidly increasing among women and youth. Oral cancer victims and survivors may be valuable in such public campaigns.
- Secondary prevention: screening: Screening for oral cancer by visual examination of the mouth has been researched in several countries, usually with the conclusion that it is not cost-effective. In the majority of cases in India, there is a recognisable precursory phase. Visual inspection with sufficient light and has demonstrated a reduction in mortality at modest cost.
- Pain control and palliative care : Oral cancer causes severe physical, psychosocial and spiritual pain to patients and their families. Trained staff and facilities for caring for terminally ill patients and their families are required across the nation
Oral cancer is a multidimensional problem that has immense impact on individuals and their families, on all health services and on wider society. We recommend the adoption of a diagonal approach to treatment and prevention that is fully integrated into primary care and into the existing activities of the many relevant medical, religious and social organisations. We need to reorient oral health research, practice and policy towards a model based on social determinants and support closer collaboration between, and integration of, dental and general health research.Efforts towards the control of oral cancer in India will benefit from an approach based on common risk factors that integrates oral health with overall health care and applies existing knowledge in a whole-society approach. Ever-present funding constraints and lack of political will in the field of health care must be challenged by continued and innovative advocacy.
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© 2021 Soumya Bhattacharjee