Actinic keratoses (= solar keratoses, AK, SK) are pre-malignant (pre-cancerous) skin lesions with the potential to develop into cancer (squamous cell carcinoma, SCC). Actinic keratoses are the result of long-term sun over-exposure and sun damage. They are extremely common lesions, especially on the sun-exposed skin of fair-skinned people. More than 80% occur on the head and neck, back of the hands and forearms. Advancing age, male sex, outdoor occupation or hobbies are all risk factors.
Examples of Actinic Keratoses / Solar Keratoses
Some consider AK to be one stage of a continuum of malignant change starting with UV-induced DNA damage followed by neoplastic transformation followed by proliferation and invasion to SCC followed by metastasis and death
Not all AKs progress to SCC
Estimates for transformation have ranged from 0.1% to 26.7%.
Perhaps a more realistic figure is 1-2%
Usually actinic keratoses appear as small, brown, pink or whitish, scaly erythematous [red] single or multiple rough spots smaller than 1cm in diameter. They may be flesh-toned, pink or brown and typically present on sun-exposed sites. They feel rough or cause soreness, irritation, discomfort or pain or they may just pose a cosmetic nuisance.
Treatment of Actinic Keratoses
Practically, it is impossible to treat all AK. Approximately 25% of AK may spontaneously disappear. But knowing which will involute is impossible, so most physicians will treat AKs. The choice depends on the location and number of lesion, the individual and the experience of the physician with the treatment modalities.
For small individual lesions or a small number of lesions probably the treatment of first choice is cryotherapy. This is liquid nitrogen destruction of AK and is a quick and easily performed technique with cure rates up to 95-100%.
Patients tolerate cryotherapy for their solar keratoses well with few side effects
There are several methods for applying the cryogen – Open Spray gun or cotton bud
Diclofenac sodium in hyaluronan gel [Solaraze]
A good treatment for thin AK.
Needs to be applied thinly bd for 60-90 days
Chemotherapy - 5-FU, Efudix
see SKCIN Trustee John Holmes being treated with Efudix for his AKs.[www.bbc.co.uk/nottingham]
This is a safe and highly effective treatment for AK. 5-FU spares normal skin but can “light-up” clinically inapparent or early AK. However, treatment can be long and produce inflammation at the site of the AK resulting in prolonged redness and unsightly and sore erosions. It is available as Efudix cream and suited to the treatment of multiple AKs.
Safe and effective with cure rates up to 93%
The usual duration of initial treatment 3-4 weeks
Successful treatment can entails erythema, vesiculation, erosions, ulceration, necrosis and then re-epithelialisation
Unfortunately lower cure rate are reported when patients cannot comply or the medication is used improperly. Treatment failures as high as 60% have been reported.
sunlight can cause pain and discomfort at the sites being treated.
Curettage and cautery
”scrape and burn”. This technique uses a curette to mechanically scrape away the AK’s atypical cells then cauterises the base and is an excellent way to treat AK. It offers high cure rates with excellent cosmetic outcomes. It is a safe and effective treatment for AK. Curettage is effective for almost all clinical types of AK but is particularly useful for those lesions thought to be closer to invasive squamous cell carcinoma (SCC), lesions resistant to other treatments, and after biopsy. Disadvantage of curettage is that a local anaesthetic is required. If the skin is burned too rigorously a scar can result. Infection and other complications are rare
Generally surgery is unnecessary but there are exceptions. Bleeding, induration, rapid growth, or pain suggest progression to SCC or when AK are very thick or resemble cutaneous horns, hyperkeratotic AK or where invasive squamous cell carcinoma is suspected or where the diagnosis is in doubt.
Topical PDT results in almost universal initial clearance. Recurrence rates at 12 months vary between 28% and 0%. Treatment of the scalp can be extremely painful. Treatment of solar keratoses with PDT appears to be as effective as 5-fluorouracil. This is available in some NHS hospitals and is time-consuming thereby limiting its use.
In extensive disease PDT can have an advantage as PDT is capable of treating multiple lesions or areas that amounting to a “field change” for example on the dorsae of the hands of scalp.
If a lesion does not respond to treatments for AK, then biopsy should be considered to exclude SCC. The benefits of sunscreen and modifying solar exposure are important