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Block 2 - MSK > Lecture 22 - Prevention Of Skin Cancer > Flashcards

Lecture 22 - Prevention Of Skin Cancer Flashcards

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
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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
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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
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4
Q

Actinic keratoses

A
  • sunspots
  • > 60% of Australians over 40
  • Premalignant: can progress to SCC
  • may spontaneously resolbe
  • tenderness may indicate progression
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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
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6
Q

What causes skin cancer

A
  • DNA damage
  • immunosuppression
  • UV induced DNA damage or immunosuppression
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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
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8
Q

BCC risk factor

A
  • episodic/recreational UV
  • sunburns
  • immunosuppression
  • Genetic: Xeroderma pigmentosum or Gorlin syndrome
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9
Q

Carcinogenic

A
  • arsenic
  • UV
  • radiotherapy
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10
Q

SCC risk factor

A
  • chronic UV exposure
  • up to 80% of SCC arise from AK
  • immunosuppression
  • HPV is a cocarniogenic with UV
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11
Q

Skin cancer prevention goals

A
  • prevent DNA damage
  • protect skin immunifty
  • enhance DNA repair
  • replenish cellular energy
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12
Q

Skin cancer prevention strategies

A
  • minimise UV exposure
  • sunscreen
  • chemoprevention
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13
Q

UV minimisation

A
  • avoid sunburn
  • sunglasses: prevent peripheral light focusing
  • shade
  • hats
  • tightly woven clothing
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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
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15
Q

Stress and skin cancer

A
  • acute stress bumps up immunity

- chronic stress increases photocarcinogenesis

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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
Q

Other chemopreventers: Retinoids (VitA related)

A
  • acitrecin in transplant patient
  • can have liver, lipid and bone side effects
  • dry skin, dry lips, hair loss, teratogenic
26
Q

Other chemopreventers: COX inhibitors

A
  • opical NSAIDS: diclofenac gel for AK
  • decrease SCC in people taking aspirin/NSAIDS
  • 40% reduction in BCC/SCC with celcoxib
27
Q

DNA repair enhancers

A
  • T4N5 liposomes

- decrease AK, BCC in xeroderma pigmentosum patients

28
Q

Nicotinamide

A
  • 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
Q

Pellagra symptoms:

A
  • diarrhoea
  • dementia
  • dermatitis
30
Q

Nicotamide effects

A
  • UV protective in mice: prevent UV immunosuppression and photocarcinogenesis
  • prevent UV immunosuppression in humans
  • gives broad spectrum immune protection
31
Q

How does nicotinamide work?

A
  • 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
Q

Can nicotinamide prevent skin cancer

A
  • 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
Q

Benefits of nicotinamide

A
  • well tolerated
  • cheap
  • already widely available
34
Q

Nicotinamide in the clinic

A
  • for patients who have already had multiple (non-melanoma) skin cancers)
  • no evidence of efficacy in low risk people
35
Q

Men and sun protection

A
  • men are immunologically weaker
  • testosterone is immune suppressive: men a re more susceptible to UV immunosuppression
  • higher skin cancer incidence and mortality
36
Q

Secondary prevention

A
  • a history of skin cancer greatly enhances the risk of further skin cancers
  • only 50% of ONTRAC patients have recently used sunscreen

Block 2 - MSK (38 decks)

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