Solar keratoses

Risk factors for solar keratoses

Risk factors include:

• Long term exposure to ultraviolet radiation: usually long periods of time spent in the sun over many years.
• Fair skin.
• Increasing age.
• Smoking.

Solar keratoses and skin cancer

Solar keratoses usually are not a serious health problem. Most remain unchanged without treatment, and many disappear by themselves.

A small proportion (about 5-10%) develop into squamous cell carcinoma within ten years. Squamous cell carcinoma, while usually easily cured, can potentially be serious. It is almost always far more difficult to treat than solar keratoses, so early treatment of solar keratoses is usually recommended.

Field cancerisation

When there are many solar keratoses over a body region and the process of developing into skin cancer has commenced in some of them, the skin is said to have field cancerisation. This condition indicates a high risk of skin cancer and the entire area should be treated medically.

Treatment of solar keratoses

Several treatments are available for solar keratoses. They have different side effects, ease of use, success rates and costs. You should discuss the risks and benefits with your doctor and select a treatment or combination of treatments that suits your condition and preferences.

Lesion treatment vs. field treatment

Solar keratoses treatment can focus on individual sun spots (lesions) or the entire affected area (field).

• Field treatment – applying a cream to the area – works better, and the effects last longer than treating individual solar keratoses, but it takes longer, often has unpleasant side effects and is more expensive.
• Lesion treatment – where a doctor treats individual solar keratoses by cryotherapy (freezing) or diathermy (burning) – is inexpensive, convenient and quick, but it can cause blisters, skin colour change and, rarely, scars. Some people find it painful.

Your doctor will help you decide on the best treatment for your situation.

Cryotherapy (freezing)

A doctor freezes individual spots using liquid nitrogen. This is an inexpensive one-off treatment and is useful for people with a small number of solar keratoses. It’s not useful for treating subclinical solar keratoses.

This is a popular option for people who want to have treatment on the spot and not worry about applying creams or ointments later.

Cryotherapy tends to cause a burn-like effect in treated areas with redness and blisters, which take 2-3 weeks to heal. A small number of people (less than five per cent) develop pigmentation changes (either more or less pigmentation) at treated sites.

Field treatment with prescription creams and ointments

People with many solar keratoses may get better results from applying a cream to affected areas rather than treating individual spots (field treatment). Field treatment can eliminate subclinical (invisible) spots, and the recurrence rate is lower than that of individual spot treatment.

“Field treatment can get rid of subclinical (invisible) spots and the recurrence rate is lower than with individual spot treatment.”

The field treatment most commonly used in Australia is a chemotherapy agent applied to the affected area once or twice daily for up to 4-5 weeks. This treatment causes irritation and redness of the skin during the period of treatment and sun exposure must be avoided during this time. However, of all the treatments, it has been shown to result in the greatest patient satisfaction 12 months later.

An exciting new treatment is a combination cream containing the chemotherapy agent mentioned above plus a form of vitamin D, which acts as an immune system stimulator.

This combination works as effectively as the original chemotherapy drug by itself with the advantage that most solar keratoses can be effectively treated in only 4-6 days.

A further benefit of this treatment is that skin cancers are less likely to develop in the treated area for three years. This combination is not readily available in most pharmacies and must be prescribed by a doctor and prepared by a compounding pharmacy.

Side effects of all the field treatments include redness and sometimes blistering of the skin. These effects usually clear up about two weeks after completing the treatment.

Photodynamic therapy (PDT)

Photodynamic therapy is a combination treatment where a topical cream is activated by light. It is a useful treatment if there are multiple solar keratoses and a single one-off treatment is preferred rather than repeatedly applying a cream.

Photodynamic therapy involves several steps performed at the clinic over several hours:

1. Preparation of the skin.
2. Application of aminolevulinic acid cream.
3. Waiting for the cream to penetrate into the skin.
4. Activating the cream with light, either red light LED phototherapy or intense pulsed light. Sometimes, both lights are used in combination.

Fractional laser treatment

Fractional laser treatment creates small pockets of skin damage, breaking down abnormal tissue and encouraging the growth of normal skin cells in its place.

This treatment is useful as a field treatment because of its shorter period of inflammation and downtime than topical or photodynamic therapies. Added benefits include smoother, clearer skin after treatment and there is emerging evidence that for some patients, fractional laser therapy may reduce the incidence of future skin cancers in the treated area.

“Added benefits include smoother, clearer skin after treatment and there is emerging evidence that for some patients, fractional laser therapy may reduce the incidence of future skin cancers in the treated area.”

Electrocautery (burning)

Like cryotherapy, this treatment is used on individual sun spots. It involves burning the spots and is useful for especially thick and crusty sun spots because it penetrates deeper than cryotherapy.

Electrocautery (sometimes known as diathermy) is usually done under local anaesthetic and limited to one or two spots at a time.

It has a higher risk of scarring than other treatments.

Tea tree oil

Recent research has shown that some people have successfully treated solar keratoses with tea tree oil, experiencing fewer side effects than with other treatments. The best results have been achieved specially-formulated products specifically developed for skin treatment. These products are not yet considered a mainstream treatment for solar keratoses.

Salicylic acid

Salicylic acid creams and shampoos can help break down the thick, crusty top layer that often appears on solar keratoses. By itself, salicylic acid is not an effective treatment for solar keratoses, but your doctor may recommend you use it on the affected area prior to using other treatments.

Prevention of solar keratoses

Solar keratoses occur mainly in fair skinned people with a history of many sun exposures over a long period. This means that once you have been diagnosed with solar keratoses, you are likely to develop more in future.

You can reduce the number of future solar keratoses by minimising your sun exposure during high risk times. Using SPF 30-50+ broad spectrum sunscreens, as well as protective hats, long sleeves and pants, can improve the general condition of your skin as well as reduce the risk of skin cancers.

Vitamin B3 (nicotinamide) tablets

Vitamin B3 (nicotinamide), taken orally, helps treat solar keratoses. It has been shown to reduce existing solar keratoses by about 30 per cent, so it is most useful in combination with other treatments.

Vitamin B3 may also help prevent basal and squamous cell carcinomas in people at high risk (including those with many solar keratoses). Further research is necessary to determine the effect in people at lower risk.

Update

Recent research has suggested that very high doses of vitamin B3 may be broken down into compounds that might possibly increase the risk of cardiovascular conditions (e.g. heart attack and stroke) in some patients. This means if you are considering taking vitamin B3, you should discuss the risks and benefits with your doctor.