Solar keratoses, also known as actinic keratoses (AK) are precancerous lesions on the skin caused by chronic exposure to UV damage. The majority of Australians with fairer skin types will have a significant actinic keratosis load by their 6th decade of life and represent an increased risk of squamous cell skin cancer (SCC).
Solar Keratosis
When chronically exposed skin is repeatedly damaged it causes proliferation of the outside layer of skin cells called keratinocytes with varying degrees of change (dysplasia). If the outer layer of skin (epidermis) is filled with these cell changes then we call this a squamous cell carcinoma in situ or Bowens disease. These lesions are thought to offer a 5% risk of penetrating the deeper layers as an invasive SCC.
Solar keratosis presents as small, scaly, rough patches on the skin’s surface. Visible lesions may be surrounded by tissue that clinically appears normal but has significant UV-induced histologic abnormality. We call this field cancerisation.
So when solar keratosis exists as early sun damage we have an opportunity to avoid progression to SCC. This can be done in various ways.
Cryotherapy – clearance 40-50%. Painful, scarring. We don’t recommend this for lesions on the face.
| Treatment | Duration of treatment | Duration of Reaction | Clearance efficiency | Cost | Side effects |
|---|---|---|---|---|---|
| Cryotherapy | Instant | 48 hours | 40-50% | $ | Pain, white scar |
| Photodynamic Therapy | 3 hours | 5-7 days | 60-65% | $$$$ | Localised Sunburn appearance |
| Efudix | 3 weeks | 4-5 weeks | 70% | $$ | Scabbing, weeping, painful, need to stay out of the sun |
| 5FU/Cal (Efucal) | 4-6 days | 9-12 days | 75% | $$ | As above but often milder |
| Imiquimod / Aldara | 3 weeks per treatment at least 6 weeks | 6-12 weeks | 55-60% | $$$ | Flu like symptoms |
Topical Therapies
Efudix 70% clearance rates at 12 months, effect seems to wane at 3 years. 3 week application. Can be a severe reaction
5FU/VitD 75% clearance rates, data to 3 years shows maintained effect. 4-6 day application. Severe reaction less common.
Imiquimod 50-65% clearance rates, immune modulated viral like illness common, pulsing therapy 3 weekly for up to 12 weeks. Not listed on PBS for AK treatment.
Photodynamic Therapy – 60-65% clearance rates. One use, milder reaction like a sunburn. Can use sunlight to activate cream which is less painful than UV light applications in clinic.
Sun protection – Nambour Study showed that 50% of solar keratosis could be regressed in 6 months of complete sun protection with daily sunscreen. It is thought that the body’s own immune system can heal much of this damage when allowed to rest from UV damage. This is likely why compared to Euopean countries with deep winters, Australia sees such a huge increase risk of SCC.
During your skin check your doctor may discuss these treatment options. A fundamental belief at The Skin Cancer Clinic Claremont is prevention of skin cancers. Treating early sun damage in an excellent prevention strategy.
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