UVR causes ‘signature’ mutations in our DNA. These DNA abnormalities are often repaired, but increasing numbers of abnormalities due to increasing UVR exposure may overwhelm the repair mechanisms, causing skin cancer.
There are two main categories of skin cancer – ‘melanoma’ (also known as ‘malignant melanoma’) and ‘non-melanoma skin cancer’. NMSC mainly comprises ‘basal cell carcinoma’ (BCC), which is the most common and least dangerous form, and ‘squamous cell carcinoma’ (SCC), which accounts for about a fifth of all NMSCs.
In the UK, more than 70,000 new cases of skin cancer are diagnosed annually, making it the most common cancer. In fact, the actual figure is thought to be over 100,000 new cases a year, but traditional cancer registries often exclude NMSC or are at least incomplete, so incidence data for NMSC is lacking. Of these new cases, 9,000 are melanoma. There are over 2,300 deaths from skin cancer annually in the UK, of which 1,800 are from melanoma and 500 from non-melanoma skin cancer.
Skin cancer is most common in fair-skinned people, especially those with blue eyes, skin type I and II (sunburn easily, suntan poorly, freckle with sun exposure), and red or blond hair. Over 80 percent of NMSCs occur on the head, neck and forearms, corresponding to the areas most exposed to sunlight. Tumours are often multiple.
The incidence of all types of skin cancer has more than doubled over the past decade, which is widely believed to be due to social changes, including increased UV exposure from both the sun and artifi cial sources.
Sunscreen plays an important role in the armoury of sun protection methods. Product labelling has recently changed, following a 2006 EU recommendation about claims relating to their efficacy.
Dermatologists generally divide skin types into six categories, from phototype I – fair skin that burns very easily in the sun and does not tan - to phototype VI, which is darker black skin that does not burn easily. People with a darker complexion have more natural sun protection, while fair-skinned individuals are more susceptible to sun burn, skin cancer and photodamage.
The use of clothing and sunscreen applies to skin types I and II at all times in the sun, and to skin types V and VI during periods of prolonged or intense sun exposure. Darker skin types do not need to routinely use sunscreens.
The main types of UVR to reach the earth’s surface are UVB (which causes sunburn, and therefore has strong links to malignant melanoma and basal cell carcinoma risk) and UVA (which contributes to skin ageing, as well as skin cancer, although to a lesser degree than UVB).
Sunscreens in the UK are labelled with a ‘sun protection factor’ (SPF), although the SPF is more accurately the sun burn protection factor, as it primarily shows the level of protection against UVB, not UVA.
UVA protection is shown through a ‘star’ system and/or a UVA logo. The UVA stars range from 0-5 and indicate the percentage of UVA radiation absorbed by the sunscreen in comparison to UVB. In other words, the ratio between the level of protection afforded by the UVB protection and the UVA protection.
It is therefore possible for a product with a low SPF to concurrently have a high level of stars, because the ratio between the UVA and UVB protection is about the same. Customers should choose a high SPF as well as high UVA protection. Sunscreens with both UVA and UVB protection are called ‘broad spectrum’.
New sunscreen labelling
The SPF and star rating systems have been criticised as being complicated and unintelligible. To combat this, the new EU recommendation has introduced changes to the labelling on sunscreens. Now, as well as the SPF number, the SPFs will be categorised as providing low to very high protection, to make the SPF guide easier to understand. According to the EU Recommendation, the UVA protection for each sunscreen should be at least a third of the labelled SPF. A product that achieves this requirement will be labelled with a UVA logo, the letters “UVA” printed in a circle:
The British Association of Dermatologists recommends the use of a high protection sunscreen (SPF 30+) with a high level of UVA protection also (four or more stars or the UVA logo). Sunscreens should not be used as an alternative to clothing and shade, rather they offer additional protection. For children or high risk groups for skin cancer, advise use of a very high protection sunscreen of SPF 50+.
Studies have found that most people apply less than half of the amount required to provide the level of protection indicated on the packaging, and that sites such as the back and sides of the neck, temples and ears are commonly missed. It is hard to say exactly how much to apply as sunscreens are available in a range of different formulas, including lotions, sprays and gels.
Individual manufacturers can provide further details, but when using lotions, as the bare minimum customers need to apply at least six full teaspoons (approximately 36 grams) to cover the body of an average adult. The overall message in terms of sunscreen use is ‘more is better’. Sunscreen should be applied shortly before sun exposure starts and then again half an hour after, and reapplied at least every two hours.
Signs of skin cancer
As there are several different types of skin cancer and each has different and varying symptoms, it is hard for the untrained eye to know what is, and is not, a cancer.
Most BCCs are painless. People often first become aware of them as a scab that bleeds occasionally and does not heal completely. Some look like a scaly red flat mark; others have a pearl-like rim surrounding a central crater. Others are quite lumpy, with one or more shiny nodules crossed by small but easily seen blood vessels.
An SCC usually appears as a scaly or crusty area of skin, with a red, inflamed base. Most are not painful. A third of all melanomas develop in existing moles but the rest arise from normal skin. Therefore a new, changing mole, particularly over the age of 30, should be considered suspicious.
In terms of changes to a mole, major features of melanoma are:
- Change in size;
- Irregular shape;
- Irregular colour.
Minor features are:
- Largest diameter 7 mm or more;
- Oozing / crusting;
- Change in sensation.
To help educate the public about suspicious lesions, the British Association of Dermatologists uses its ‘ABCD-Easy rules to mole checking’.
Sun safety tips
While sunscreen is important, it should not be used as the sole method of sun protection. Clothing and shade should take priority. People do not have to avoid the sun all year, but taking a few steps when out and about in the summer sun or when on a sunshine holiday will help to protect the skin from sunburn and the risk of skin cancer.
- Protect the skin with clothing, including a hat, T-shirt and UV protective sunglasses;
- Spend time in the shade between 11am and 3pm when it’s sunny;
- Use a sunscreen of at least SPF 30 (SPF 50 for children or people with pale skin) which also has high UVA protection;
- Keep babies and young children out of direct sunlight as they burn more easily than adults and can also overheat.
Sun Awareness is the British Association of Dermatologists’ annual skin cancer campaign. For information about prevention and detection, and free leaflets and posters, visit: www.bad.org.uk/sunawareness
Dr David Eedy is consultant dermatologist with the Craigavon Area Hospital Group Trust, and Honorary Secretary of the British Association of Dermatologists.