Actinic Keratosis – Solar Keratosis
They are found on chronically sun exposed surfaces of the skin. Highest risk factor is sun exposure; especially on light skin individuals in sunny lands close to the equator or higher elevation. Genetic factors (p53 mutation), a link to viruses (HPV), immunosuppression, and the degree of skin pigmentation has also been associated with an increase in risk.
Solar irradiation not only damages DNA of keratinocytes, but diminishes the immune response to repair it.
In adults 40 years and over, as many as 6 out of 10 cases of squamous cell carcinoma begin as untreated AKs. This type of skin cancer can become life-threatening.
Millions of Americans have AKs—and this number is increasing because most people do not use adequate sun protection.
Actinic Keratosis is best recognized on inspection and palpation (touching). Studies report that 5 to 20% of AK’s may develop into a squamous cell carcinoma. It may take ten to twenty years for actinic lesions to progress into a SCC
One thing is clear, when a SCC is diagnosed, there is evidence of actinic damage. Hence, treating AK’s before they evolve is recommended.
Treatment with Cryotherapy is most effective and practical when treating a limited number of sites. The treatment involves application of liquid nitrogen in short bursts alternating with a thaw creating a frost. Lesions may take one to four weeks to heal depending on the site and size of the lesion. Treatment may need to be repeated every 3 months. Lesions that do not heal should be biopsied.
Other treatments for Actinic Keratosis differ in their mechanism of action. Any treatment requires avoidance of the sun until the area heals.
Photodynamic Therapy (PDT) is the application of 20% aminolevulinic acid. The ALA is absorbed into the damaged cell and is then activated by light destroying it.
5-fluorouracil (Efudex 2 & 5%, Carac 0.5) is topical chemotherapy to produce a severe inflammatory reaction. Application is once to twice daily for 3 to 6 weeks. Treatment is stopped once the reaction to produced. Some people cannot metabolize the drug (DPD enzyme deficiency) and get a severe reaction within the first few days. Those individual should not use this medication.
Imiquimod (Aldara 2.5% & Zyclara 3.75%) uses the application of a drug to ignite the immune response. The treatment is comprised of daily application of twice a week for 16 weeks. The higher strength is daily application for 2 weeks, followed by a 2 week“rest period”and then re-application for another 2 weeks.
Diclofenac (Solaraze 3%) uses the twice daily topical application of a drug that inhibits prostaglandin. Cells need prostaglandin to survive. Treatment with this drug is for 60 – 90 days.