By Luis Enrique Cam

Introduction

Oral pre-cancer and cancer are potentially the most damaging of oral diseases due to the serious nature of these lesions that could lead to the death of the individual, therefore, the early identification of them is critical (Gift 1993). One of the principal aims of screening a population is to detect the disease or predictors of the disease at an early stage. In the context of oral cancer prevention, screening can be considered so as to identify people who are at high risk in order to carry out an early treatment intervention.The purpose of this essay is to apply the principles of screening to oral cancer so as to assess the value of a screening examination and if recommendable, to implement it. The high risk population of this disease is described as well. Finally, a hypothetical screening programme for oral cancer in Peru is discussed.

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Oral Cancer

The term oral cancer is considered to be malignant neoplasm and include cancers of the lip, tongue, mouth and pharynx (British Dental Association 2000). Ninety five per cent of malignant neoplasms in the oral cavity are squamous cell carcinomas of the oral mucosa, tongue and lips. The disease is almost twice as common in men as in women (FDI 1999). In Peru, the National Institute of Neoplasms Diseases (INEN) receives between 160-180 new cases of oral cancer annually. This centre receives patients from all parts of the country but not necessarily all cases are reported to them. For the intraoral disease the two main risk factors are tobacco use and alcohol consumption (Macfarlane, 1993),with there being evidence that their combined effects act synergistically to increase the risk of oral cancer (CRC 1990), which together cause 75-90% of all cases. In 2003, almost 1,600 people in the UK died from mouth cancer. Overall, death rates have decreased little since the 1970s. While the death rate has halved for men in their 70s and 80s, it has steadily increased for younger men aged 30-50. Survival rates vary depending on the type of mouth cancer. But for all types, survival greatly improves if the disease is detected at an early stage. For example, for patients with tumours in the mouth cavity, two-year survival rates are:

  • just under 90% if detected early (stage I); and
  • under 50% if detected after they have spread (stage IV).

Almost all cases of mouth cancer are preventable. 80% of cases are thought to be due to tobacco, alcohol or a combination of both. Unhealthy diets may account for 10-15% of cases (Cancer Research UK 2005). Aetiology of oral cancer:

Established risk factors

  • Smoking tobacco.
  • Chewing tobacco/oral snuff.
  • Chewing betel quid (pan) with tobacco.
  • Heavy consumption of alcohol.
  • Presence of potentially malignant lesions.

Predisposing factors

  • Dietary deficiencies (vitamins A, C, and E, and iron).
  • Genetic disposition.
  • Sunlight (lip cancer).
  • Dental Trauma.
  • Viral Infections.

Certain oral lesion such as leukoplakia and eritroplakia can precede the development of malignancies. The rate of malignant transformation from leukoplakia is very low, at 5% (Schepman K. et al. 1998).

Screening

Screening has been defined as ‘the presumptive identification of unrecognized disease or detect by application of test, examination or other procedures which can be applied rapidly’ (Commission on Chronic Illness 1957).Screening offers to test selected population groups who are apparently healthy with the purpose of separating them into groups having high and low probability for a particular disorder. The offer to screen and be screened must be made with the belief that those who volunteer will benefit from the process (Wilson and Jungner 1968).The principal aim of screening is to identify a disease in apparently healthy asymptomatic individuals before they would normally be present with symptoms in order to offer further investigations, preventive advice or treatment.Wilson and Jounger (1968) described ten principles of screening:

  1. The condition should be an important health problem.
  2. There should be an accepted treatment for patients with the recognized disease.
  3. Facilities for diagnosis and treatment should be available.
  4. There should be a recognizable latent or early symptomatic stage.
  5. There should be a suitable examination.
  6. The test should be acceptable to the population
  7. The natural history of the disease should be adequately understood.
  8. There should be an agreed policy on whom to treat as patients.
  9. The cost of case-finding should be economically balanced in relation to possible expenditure on medical care as a whole.
  10. Case finding should be a continuous process and not a ‘once and for all’ project.

Some requirements before launching a screening programme is to consider whether the cost-benefit and cost-effectiveness of the programme are favourable (Scheutz 2001). Holland and Stewart (1990) described four types of screening:

  1. Screening for individuals with risk factors which predispose them to the disease but are not in themselves alerting symptoms.
  2. Screening for individuals with early signs of the disease.
  3. Screening for individuals for which preventive action could be taken to restore health.
  4. Screening for established diseases that could be alleviated by continuous care and surveillance.

Discussion

In order to implement a strategy to tackle oral cancer in the population it would be important in applying the principles of screening to oral cancer to evaluate its efficacy. Head and neck cancer (oral cancer included) meets some principles of screening but not all the criteria. Moreover, although there are clear potential advantages for screening, there are also potential disadvantages (Johnson, 2002. Oxford Textbook of oncology).

Potential Advantages of screening

Reduce mortality. Reduce incidence of invasive cancer. Improved prognosis for individual patients. Reduce morbidity from earlier treatment. Identification of high risk individuals/groups allowing targeted prevention. Reassurance for those screening as negative. Cost saving from expensive treatments.

Potential Disadvantages of screening

Detections of cases already incurable may increase morbidity for some. Unnecessary treatment for pre-malignant lesion which might not progress. Psychological trauma to those with a false-positive result. Reinforcing bad habits amongst some individuals screened as negative. Costs. The rationale for screening is based on the fact that these cancers may be asymptomatic and localized for a period of their natural history, and are preceded by potentially malignant lesions and conditions such as leucoplakia, erythroplakia, and submucous fibrosis, when they might be detected by simple systematic clinical examinations. This is important because habit intervention, (Grupta et al. 1995) dietary intervention, (Sankaranarayanan R, et al. 1977) and surgical treatment may result in their resolution or elimination.However, national screening programmes cannot be recommended (Speight et al. 1993) because there is inadequate understanding of natural history and there is insufficient evidence of utility(Downer 1997) or cost-effectiveness like those for breast and cervical cancer for example, without further research. Oral-cancer screening programmes have been carried out on several hundreds of thousands of individuals in developing countries (mostly Sri Lanka, India, and Cuba) and several thousands in developed countries (mostly the United States, United Kingdom, and Italy)—the evidence from these screenings were reviewed by Warnakulasuriya and Johnson. In the high-incidence parts of the world, a substantial proportion of suspicious lesions have been found (ranging from 2 to 16 per cent in south Asia) but the compliance of patients to attend follow-up was poor. The yield is substantially lower in the West. For example, the largest study group comprised over 23,000 adults in Minnesota over 30 years of age whose mouths were examined by dentists between 1957 to 1972. Although more than 10 per cent of those screened had an oral lesion, these were mostly benign: ‘pre-cancer’ was encountered in 2.9 per cent and cancer in less than 0.1 per cent. (Johnson, N. Oxford Textbook on Oncology 2002). A stronger case may be made for targeting screening to at-risk populations—for head and neck cancer perhaps to smokers and heavy drinkers over the age of, say, 40 years. Such individuals can be identified from the records of family medical practitioners, or occupational health records. Even so, studies of this kind conducted in the United Kingdom and in Japan have shown high non-attendance rates for the initial oral examination. This, together with the low prevalence of lesions, makes even this type of screening of dubious utility. Recently, the Oral Cancer Screening Group at the Eastman Dental Institute, London, has carried out an outstanding series of investigations. One of these studies suggests that patients attending general dental practices that had participated in the study were representative of the general population both in terms of lesion prevalence and high risk habits such as smoking and drinking. This supports the view that opportunistic screening in a general dental practice setting may be a realistic alternative to population screening. However, further research is needed to determine the cost effectiveness of this approach and to investigate the value of targeting high risk groups within this population (Lim et al. 2003).

Target for Oral Cancer Screening

Population screening cannot be recommended for oral cancer because of the insufficient evidence of utility as we saw above.– Knowing the two most important risk factors associated with oral cancer: high consumption of tobacco and alcohol which cause 75-90% of all cases, it would be recommended targeting these populations to perform a screening for oral cancer.

Screening Programme in Peru

If a screening programme for oral cancer was implemented in Peru, these recommendations should be followed: Each general dentist should be trained by the Ministry of Health in order to be advised of the criteria of a positive and negative screen. Patients attending a routine dental or health check-up, who are over the age of 35 with smoking and drinking habits, should be asked to be screened. Dentists should examine the soft tissues and record the presence or absence of lesions in the medical history. Dentists should advice and support their patients in adopting healthier choices, like: 1) stop smoking; 2) be moderate in alcohol use (3 units daily maximum); and 3) eat five or more portions of fresh fruit and vegetables a day. From a population approach, it would be useful to conduct a public campaign to promote the screening programme among deprived communities where the alcohol consumption is high, particularly in the highlands and suburban areas.

References

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