UV and You
In the Car
Glass blocks essentially all UVB but transmits variable amounts of UVA. Laminated glass in windscreens blocks 98% of UVA. Tempered glass in side windows however may only block as little as 20% of UVA. This is one reason why skin cancer is more frequent on the right hand side in Australians.
Total Body Photography
The commonest kind of melanoma found on a skin check is Melanoma In Situ which is a very early melanoma that grows slowly over years and develops into more aggressive melanoma with a frequency that is at present unknown. While it remains Melanoma In Situ, it only jumps to another site (metastasises) rarely. It can be very subtle even under the dermatoscope, in fact even for the pathologist under the microscope. On skin with a lot of moles it can be difficult to pick up the subtle lesions of Melanoma In Situ or even more advanced Melanoma. In theory at least, these lesions might be found earlier using Total Body Photography year on year to detect new or growing lesions. We know how to monitor one lesion with photographs to exclude melanoma but there is little evidence to tell us how effective Total Body Photography actually is. It is thought to be a very good idea for people with lots of irregular shaped moles. At NSGP we are not currently able to take these photographs but total body photography is available locally.
How often should you have a skin check?
There is no direct evidence to guide us here but recommendations vary by only a little. Go to the SCAN website for the Skin Cancer College of Au & NZ recommendation for your level of risk of skin cancer: http://www.scanyourskin.org/risk-prediction-tool/
If your risk is low, the consensus is that it would be reasonable to have a skin check every two years but you should check your own skin every year. Not everyone is confident or able to check their own skin however, so it isn’t unreasonable to attend for a skin check instead. If you have risk factors, an annual skin check is the consensus recommendation, especially after the age of 50. If you are at high risk 6 monthly checks are recommended. Your risk of skin cancer continues to increase every year of your life while the risk for melanoma, from childhood exposure to UV, stays with you.
In some cases skin checks are done more frequently. Some people get frequent BCCs so have checks every 6 months. After a Melanoma is treated checks are done every 6 months for 2 years in the case of Melanoma In Situ and annually thereafter; or every 3 months for 2 years and annually thereafter for deeper melanoma. After you have one melanoma, you are 5 times more likely to get another melanoma than an average person is to get their first melanoma. People on immune suppressant drugs are at much greater risk of SCC so are recommended to have skin checks more frequently. After organ transplant, 3 monthly checks are advisable.
What's different about Celtic Skin?
Everyone has the same number of pigment producing cells (melanocytes) in their skin. Melanocytes produce melanin and pass it to the skin cells (keratinocytes). One melanocyte gives pigment to about 10 keratinocytes. Melanocytes produce two types of pigment: eumelanin which is brown and phaeomelanin which is red. Red heads have melanocytes that produce mainly phaeomelanin, whereas for non redheads it is mainly eumelanin.
Phaeomelanin isn’t very effective at blocking UV. In northern Europe people might have evolved to have more phaeomelanin for better Vitamin D production. Red heads are much more susceptible to sunburn and skin cancer though.
Sunbeds and sunlamps are estimated to increase the risk of melanoma by 20% (in those who have ever used one) to 60% (in those who first used a sunbed before age 35). Sunbeds emit UVA which doesn’t cause sunburn but does cause skin ageing and skin cancer.
There’s plenty of information on the net about skin cancer prevention:
What can be done for brown freckles on your face?
Brown lesions on the face are mostly Solar Lentigos (SLs) and Seborrhoeic Keratoses (SebKs) coloured by increased amounts of melanin.
For SLs and thin SebKs topical treatment with Hydroquinone or Azelaic Acid can make the lesions less dark. Hydroquinone bleaches the brown colour of melanin, whereas Azelaic Acid calms melanocytes down so they stop overproducing melanin.
Cryotherapy can make these lesions less dark and is one way of removing thick SebKs, but it is difficult to judge how much freezing occurs at the base of these thick lesions and a permanent white patch may occur.
Thicker SebKs can be shaved off the skin after an injection of local anaesthetic. This approach has the advantage of yielding a specimen for the pathologist for lesions where there is room for doubt as to the diagnosis.
Cosmetic dermatologists use laser to treat these lesions with excellent results.
It is important to make sure that a lesion isn’t melanoma before any of these treatments since they may obscure the subtle signs of melanoma on the face.
Sunscreen, UV, Melanoma
This information is from a presentation by Prof David Whiteman, Berghofer Medical Research Institute.
People who use sunscreen regularly have higher rates of skin cancer! This is because they are people who have fairer skin and who spend more time outdoors. The statistics are confounded by this bias. The Nambour (Victoria) Skin Cancer Trial is the only study to compare sunscreen use with normal practice in a randomised trial, so avoiding this confounding of the data. It involved 1621 subjects over 15 years of follow-up and 33 cases of melanoma occurred (2). It showed a halving of the risk of melanoma associated with the strict use of regular daily sunscreen compared to usual practice. Sunscreen was SPF 16+ and didn’t contain Titanium or Zinc.
All the other studies are observational and put together, they show a wide range of correlations positive and negative, so unfortunately, they don’t tell us anything. But if you study the physical effects of UV exposure on the skin directly under the microscope, there is strong evidence that sunscreen protects against melanoma.
Melanoma DNA has many more mutations than other cancers and when you look at what the individual mutations are, melanoma mutations are predominantly of one kind: C to T mutations which are characteristic of the damage caused by high energy photons (UV light). This is strong evidence that UV is the cause of melanoma.
This damage occurs all the time and is repaired by DNA polymerases, but if they’re not repaired before the cell divides the mutation is passed on to daughter cells and doesn’t get repaired. If enough mutations like this accumulate in a cell it becomes cancerous.
Can sunscreen prevent these mutations? In one study by Prof Whiteman and others, enough UV was applied to small areas of human subjects’ skin to cause mild sunburn (skin types 1,2 & 3). Four things were measured in exposed skin with and without protection by sunscreen (SPF 30+): the sunburn, two biomarkers for DNA damage and melanocyte proliferation.
The biomarkers were Cyclobutane pyrimidine dimers (CPD), a biomarker for UV damage to DNA and p53 levels. p53, the “policeman of the genome”, is increased when there is DNA damage, causing the cell to go into DNA repair mode. Skin biopsies were done at baseline, at 24 hours and at 14 days.
UV exposure was enough to cause mild redness of the skin. CPD was very high in the exposed skin at 24 hours, p53 increased by a large factor and melanocytes doubled in number. At 14 days everything was back to normal. All of these effects at 24 hours were completely prevented by sunscreen.
This is one of 10 studies in the literature that have compared human skin pre and post UV exposure, looking for DNA damage, with and without sunscreen (1). All showed almost complete prevention of DNA damage by sunscreen in human skin. So we can conclude that sunscreen with SPF at least 15+ prevents biological damage to human skin by UV.
The consensus recommendation is that you apply sunscreen to exposed skin in the morning on every day when the UV index is 3 or above. That’s on average every day in Sydney except in June, all year in Queensland and 6 months of the year in the south of New Zealand.
(1) Olsen et al, Prevention of DNA damage in human skin by topical sunscreens. Photodermatology, Photoimmunology & Photomedicine (2017).
(2) Green AC, Williams GM, Logan V, et al. Reduced melanoma after regular sunscreen use: Randomized trial follow-up. J Clin Oncol. 2011;29:257–63.
(3) The effect of MC1R variants and sunscreen on the response of human melanocytes in vivo to ultraviolet radiation and implications for melanoma. Hacker et al Pigment Cell Melanoma Res. 2013 Nov;26(6):835-44
These and other melanoma facts are illustrated in the following: