OC 2- environmental aetiology

Question 1

What causes cancer?

Answer 1

all cancers result from mutations in genes

mutations in genes cause a cell to lose regulatory control so it grows at an uncontrolled rate, doesn’t repair damaged DNA and doesn’t undergo apoptosis

Question 2

Can 1 mutation turn a cell cancerous?

Answer 2

no, it takes more than one mutation to turn a cell cancerous

Question 3

How many genetic mutations have been shown to be associated with oral cancers?

Answer 3

up to 23

Question 4

What genes are often targeted by mutations?

Answer 4

tumour suppressor genes like P53 and retinoblastoma gene

Question 5

What can cause genetic errors?

Answer 5

can be inherited, can be caused by viruses, or develop as a result of exposure to chemicals or radiation

Question 6

In head and neck cancer, what are genetic errors commonly caused by?

Answer 6

viruses

Question 7

What areas can oral cancer affect?

Answer 7

the lips, salivary glands, tongue, gums, palate and inside of cheeks

Question 8

What portion of the tongue is ‘oral/mouth’ and what portion is ‘oropharyngeal’?

Answer 8

Anterior 2/3 of tongue is oral/mouth tongue

Posterior 1/3 of the tongue is oropharyngeal tongue

Question 9

What is the most common type of oral cancer?

Answer 9

Squamous cell carcinoma (90% of oral cancers)

Question 10

What can ‘head and neck’ cancers affect?

Answer 10

throat (pharynx), voice box (larynx), salivary glands, nose, sinuses, lips and skin

Question 11

Is oral cancer more common in males or females, and by what ratio?

Answer 11

more common in males, 2:1 M:F

Question 12

What are the risk factors for oral cancer?

Answer 12

• tobacco
• alcohol
• poor diet/obesity
• sunlight
• immunological defect
• previous cancer
• genetic conditions
• potentially malignant conditions
• 25% of cases have no known risk factors

Question 13

Smoking and alcohol consumption have a synergistic effect on oral cancer risk.

How much more at risk is a heavy smoker and drinker compared to a non smoker and moderate drinker?

Answer 13

24 times higher risk

Question 14

What is the most common site for oral cancer? Why?

Answer 14

under the tongue/FOM - pooling of carcinogens in the saliva

Question 15

Why does alcohol increase the risk of oral cancer?

Answer 15

Alcohol causes thinning/atrophy of the oral mucosa, making it more permeable to the carcinogens - entry of carcinogens into the epithelial cell barrier easier

Question 16

How many harmful chemicals compounds does tobacco smoke contain?

Answer 16

more than 4000

Question 17

What are the relative risks of someone who smokes <10 cig/day, <20 cig/day and >20 cig/day?

Answer 17

<10 cig/day - 2.5
<20 cig/day - 5.0
>20 cig/day - 5.5

Question 18

What is the relative risk of a current smoker vs a former smoker?

Answer 18

current smoker - 3.4
former smoker - 1.4

Question 19

Does quitting smoking ever reduce your relative risk?

Answer 19

after quitting, it takes 20 years for relative risk to be the same as that of a never smoker

Question 20

What are some of the cancer causing chemicals involved in smoking?

Answer 20

tar, arsenic, polycyclic aromatic hydrocarbons (eg. benzopyrene), nitrosamines, acrolein (mutagen, carcinogen)

other poisons in tobacco smoke include:
- hydrogen cyanide, CO, ammonia

Question 21

What is the relative risk for betel quid use?

Answer 21

2.4

Question 22

What is the relative risk for betel quid + tobacco?

Answer 22

8.5

Question 23

What is the pathogenesis for betel quid use?

Answer 23

• arecoline, an alkaloid in the nut, has been shown to stimulate collagen synthesis by 170%
• tannins present in the nut increase the resistance of collagen degradation
  -> excessive collagen build up, scarring and restriction of mouth opening
• alkaloid causes DNA damage
• lime can release reactive oxygen species from extracts of betel nut

Question 24

What is alcohol metabolised to?

Answer 24

acetaldehyde

Question 25

Where is alcohol metabolised?

Answer 25

salivary glands, mucosa, oral bacteria - hence exposure of these areas to acetaldehyde

Question 26

What enzyme breaks down ethanol?

Answer 26

alcohol dehydrogenase

Question 27

What enzyme breaks down acetaldehyde?

Answer 27

aldehyde dehydrogenase

Question 28

What are the alcohol recommendations in the UK?

Answer 28

• 14 units/week
• at least 2 alcohol free days/week
• binge M >8 units, F >6 units
• pregnancy - no safe limit, don’t drink

Question 29

Why was the alcohol limit lower for women?

Answer 29

• women’s bodies have higher proportion of body fat and less water than men = conc. of alcohol in body water is higher
• women have higher blood alcohol levels due to lower gastric ADH activity

Question 30

On average how long does it take to eliminate 1 unit of alcohol from the body?

Answer 30

1 hour (think 1 unit = 1 hour)

Question 31

What proportion of Scots binge drink?

Answer 31

1/3

Question 32

What vitamins etc. sourced from food can be effective in prevention of oral cancer?

Answer 32

• vitamin C
• vitamin E
• antioxidants
• zinc
• beta-carotene
• folate

Question 33

If someone is iron deficient, how can this increase their oral cancer risk?

Answer 33

If someone is iron deficient, they have low folate stores which can cause their mucosa to thin and increase the permeability - more readily accessible for carcinogens

Question 34

Is obesity a risk factor for oral cancer?

Answer 34

studies have suggested that obesity is linked to the risk and survival for head and neck cancers

Question 35

What factors are associated with lower lip cancer?

Answer 35

UV light, HPV, and immunosuppression