Lecture 22 - Prevention Of Skin Cancer Flashcards
(36 cards)
1
Q
Skin cancer stats
A
- life time risk in australia: 50%
- 4x as common as all other cancers combined
- costs 1 billion anually
= continues to increase in older groups
2
Q
Melanoma stats
A
- NSW: 1 in 20 (more common in men)
- Qld: 1 in 16: worlds highest incidence
- anually in Australia: 13000 new cases and 1600 deaths
3
Q
Basal cell carcinoma
A
- most common skin cancer
- 50% of Australians
- Slow growing
- almost never metastasizes
- can be quite destructive
Very different types: superficial, nodular, pigmented, micronodular, infiltrating, morphoeic
4
Q
Actinic keratoses
A
- sunspots
- > 60% of Australians over 40
- Premalignant: can progress to SCC
- may spontaneously resolbe
- tenderness may indicate progression
5
Q
Squamous cell carcinoma
A
- 2-3x less common than BCC
- can metastasize to nodes, lungs and bone
- risk depends on site, size and differentiation and host immunity
6
Q
What causes skin cancer
A
- DNA damage
- immunosuppression
- UV induced DNA damage or immunosuppression
7
Q
Melanoma risk factors
A
- acute, intermittent UV exposure in childhood, adolescence and adulthood
- some increase risk with chronic UV
- immunosuppression: 5-6x fold increase
- genetic rpedisposition
- pale skin
- multiple bland or dysplastic naevi
8
Q
BCC risk factor
A
- episodic/recreational UV
- sunburns
- immunosuppression
- Genetic: Xeroderma pigmentosum or Gorlin syndrome
9
Q
Carcinogenic
A
- arsenic
- UV
- radiotherapy
10
Q
SCC risk factor
A
- chronic UV exposure
- up to 80% of SCC arise from AK
- immunosuppression
- HPV is a cocarniogenic with UV
11
Q
Skin cancer prevention goals
A
- prevent DNA damage
- protect skin immunifty
- enhance DNA repair
- replenish cellular energy
12
Q
Skin cancer prevention strategies
A
- minimise UV exposure
- sunscreen
- chemoprevention
13
Q
UV minimisation
A
- avoid sunburn
- sunglasses: prevent peripheral light focusing
- shade
- hats
- tightly woven clothing
14
Q
Diet and skin cancer
A
- higher omega 3 and 6FA may lower skin cancer risk
- obesity and increase melanoma risk
- decrease SCC risk with leafy greens
15
Q
Stress and skin cancer
A
- acute stress bumps up immunity
- chronic stress increases photocarcinogenesis
16
Q
Smoking and skin cancer
A
- 2x risk of AK and SCC
- surgical transplants less easy
- smoking increases immunosuppression
17
Q
Sunscreens
A
- chemical absorbers: cinnamate and oxybenzone
- physical blockers: zinc oxide, titanium dioxide
18
Q
Measuring sunscreen protection from erythema: SPF
A
SPF = MED of sunscreen-protected skin / MED of unprotected skin
19
Q
Factors affecting the SPF
A
- sunscreen film thickness (people put 3x less than recomended)
- substantivity
- UV spectrum: sunlight has more UVA
- skin type
- photodecay of sunscreen active agents
20
Q
Rule of thumb for SPF
A
- real life SPF is hald the laboratory SPF
21
Q
UV immunosuppression
A
- immunosuppression increases skin cancer risk
- even low UV doses suppress skin immunity
- UV immunosuppression plays a key role in skin cancer development
22
Q
How well do sunscreens prevent immunosuppression?
A
- sunscreens are generally better at preventing sunburn than immunosuppression
- broad spectrum sunscreens (UVB and UVA) are more immune protective
23
Q
Nanoparticles in sunscreen
A
- zinc and titanium
- are harmful if you inhale them
- don’t penetrate normal stratum corneum
- UV does penetrate stratum corneum
24
Q
Do sunscreens prevent skin cancer?
A
- reduce AK/SCC risk by 40% in 2 years
- may reduce BCC and melanoma after 8 years
25
Other chemopreventers: Retinoids (VitA related)
- acitrecin in transplant patient
- can have liver, lipid and bone side effects
- dry skin, dry lips, hair loss, teratogenic
26
Other chemopreventers: COX inhibitors
- opical NSAIDS: diclofenac gel for AK
- decrease SCC in people taking aspirin/NSAIDS
- 40% reduction in BCC/SCC with celcoxib
27
DNA repair enhancers
- T4N5 liposomes
| - decrease AK, BCC in xeroderma pigmentosum patients
28
Nicotinamide
- amide form of vit B3
- precursor of NAD
- deficiency can result in pellagra
- recomended daily intake: 15-20 mg/day
- more pleasant than nicotinic acid (niacin)
29
Pellagra symptoms:
- diarrhoea
- dementia
- dermatitis
30
Nicotamide effects
- UV protective in mice: prevent UV immunosuppression and photocarcinogenesis
- prevent UV immunosuppression in humans
- gives broad spectrum immune protection
31
How does nicotinamide work?
- may replenish cellular energy -> enhance DNA repair
- enhances cellular ATP after UV -> DNA repair
- increases repair of both direct, UVB-type damage (CPD) and oxidative (UVA) DNA damage
- enhances DNA repair after arsenic and UV
32
Can nicotinamide prevent skin cancer
- 29% reduction in risk in AK by 4 months
- reduced number of neu skin cancer
- reduced skin cancer by 23% in heavily sun damaged people
- nicotinamide is only in phase 2 study.
33
Benefits of nicotinamide
- well tolerated
- cheap
- already widely available
34
Nicotinamide in the clinic
- for patients who have already had multiple (non-melanoma) skin cancers)
- no evidence of efficacy in low risk people
35
Men and sun protection
- men are immunologically weaker
- testosterone is immune suppressive: men a re more susceptible to UV immunosuppression
- higher skin cancer incidence and mortality
36
Secondary prevention
- a history of skin cancer greatly enhances the risk of further skin cancers
- only 50% of ONTRAC patients have recently used sunscreen
