Aetiology of Environmental Factors

Question 1

What causes cancer?

Answer 1

• all cancers result from mutations in genes resulting in a cell which grows and proliferates at an uncontrolled rate, is unable to repair DNA damage within itself or refuses to die
• takes more than one mutation to turn a cell cancerous
• when a cell becomes mutated, it is capable of passing on the mutations to all of its progeny when it divides
• genetic errors can be inherited, caused by viruses or develop as a result of exposure to chemicals or radiation

Question 2

What is oral cancer?

Answer 2

• cancer of the mouth: general term given to the variety of malignant tumours that develop in the mouth
• 90% squamous cell carcinomas

Anterior part - oral cancer

Posterior - oropharyngeal cancer

Question 3

What are environmental risk factors of oral cancer?

Answer 3

• tobacco, alcohol
• poor diet

0 mmunological defect

• sunlight
• previous cancer
• genetic conditions
• potentially malignant conditions
• 25% of cases have no known risk factors

Question 4

Why does smoking cause cancer?

When does RR of oral cancer compare to a non smoker after quitting smoking?

Answer 4

• cancer causing chemicals: tar, arsenic, polycyclic aromatic hydrocarbons e.g. PAH
• other poisons: hydrogen cyanide, CO, ammonia

RR = non-smoker (never) after quitting for 20 years

Question 5

How is alcohol a risk factor for oral cancer?

Answer 5

• alcohol is metabolised to acetaldehyde = mutagen and carcinogen
• metabolised in salivary glands, mucosa, oral bacteria hence exposure to acetaldehyde

Question 6

List some sources of acetaldehyde:

What are the recommended daily limit of alcohol?

Weekly?

Answer 6

• alcohol metabolism
• tobacco smoke
• bacteria associated with poor OH
• food e.g. over-ripe fruit

Daily limit = 2 units

Weekly = 14 units

At least 2 free days of alcohol/week, binge is considered more than 8 units for a male and 6 for a female

Question 7

How can poor diet influence risk of oral cancer?

How can UV light affect oral cancer?

Answer 7

• low in fruits and vegetables are effective in prevention of oral cancer
• Vit C, E, antioxidants, zinc, beta-carotene, folate

UV light:

• lip cancer
• lower lip, cracks, blisters, ulcers
• early presentation
• association with immunosuppression and HPV