Various treatments are available for AKs, and the choice of treatment should be individualized. Localized or lesion-directed therapy is best for isolated solidary lesions with no surrounding field cancerization.1 Field treatments are recommended for patients with multiple diffuse AK lesions on contiguous areas of sun-damaged skin,3 and it is advantageous in the treatment of subclinical AKs and for the prevention of further AK development.3,8 Treating both visible AK lesions and the areas of subclinical, nonvisible sun-damaged skin is critical to reducing the recurrence of AKs. 3 Field therapy alone or a combination of field and lesion-directed therapy achieves high rates of sustained lesion clearance.5 Patient preference, number and prevalence of hyperkeratotic and nonhyperkeratotic lesions, and consideration for the prevention of the development of more AKs must be considered when deciding on individual patient treatment strategies (Table 3).1,2,8

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Photodynamic Therapy

Photodynamic therapy (PDT) is a field treatment option with a mechanism of action driven by the interaction of light, a photosynthesizer, and oxygen.8 A low-molecular-weight photosynthesizer, 5-aminolevulinic acid (ALA), is synthesized in the porphyrin-heme pathway and converted endogenously into PpIX.8,9 ALA preferentially targets cells with a defective epidermal barrier. The light source, commonly blue light, excites PpIX, producing oxygen-free radicals that affect intracellular components, resulting in necrosis or apoptosis.9 The concentration of the PpIX in damaged cells destroys targeted cells while minimizing surrounding tissue damage.8,9

Initial US Food and Drug Administration clinical trials of ALA-PDT treatment of AKs on the face and scalp had a clearance rate of 85% to 90% after 2 treatment sessions (note that the treatment’s efficacy is improved with repeated PDT treatment within 30 days).8 A Cochrane review on AK treatment found PDT to be superior for eradicating lesions and resulted in preferred cosmetic outcomes, including improvement in lentigines, skin roughness, fine lines, and sallow complexion compared with cryotherapy and topical fluourouracil 5% cream (5-FU).7,8 PDT is an effective treatment with a 14% increased incidence of lesion clearance and preferred cosmetic outcomes when compared with cryosurgery on the face and scalp.7 Treatment efficacy is contingent on the proper application of the photosynthesizer.4 Cleansing the skin with acetone, chlorohexidine, or soap prior to applying ALA allows for greater photosynthesizer penetration. To increase efficacy when treating the extremities, occlusion with plastic wrap or a nonporous flexible covering enhances ALA penetration.4