Daylight Photodynamic Therapy for Actinic Keratosis and Field Cancerization: A Narrative Review

Abstract

For patients suffering from actinic keratosis (AK) and clinical evidence of chronic sun damage, achieving both actinic keratosis eradication and treating field cancerization is essential. AKs should not be underestimated. While the majority do not progress to squamous cell carcinoma (SCC), most cases of SCC develop from pre-existing AKs and nobody can differentiate between AKs that will develop into SCC and those that will either resolve on their own or remain unchanged. Photodynamic therapy (PDT) addresses AKs and also targets surrounding sun-damaged areas with precancerous cells. This dual action reduces the risk of new AK formation, making PDT a valuable approach for comprehensive skin cancer prevention in chronically sun-exposed individuals. The conventional PDT (cPDT) has already been proven a safe and effective method to treat non-hyperkeratotic actinic keratosis and field cancerization. However, in the real world, PDT has not reached its maximum potential use, possibly due to the need of an office-based light source equipment and the associated peri-procedural pain. The daylight variation of PDT (dPDT), which uses natural sunlight to activate the photosensitizer and eradicate the premalignant cells, is an effective, well-tolerated, and convenient treatment for AKs and field cancerization, with high satisfaction rates reported by both patients and physicians. Although its efficacy may be reduced in hyperkeratotic lesions and areas with insufficient sunlight, combining daylight PDT with lesion-targeted treatments and using indoor alternatives can help overcome these limitations. Additionally, the reduced peri-procedural pain and fewer topical side effects provide a significant advantage over other field treatments, such as 5-fluorouracil (5-FU), imiquimod, and cPDT, making dPDT a highly practical and accessible option in real-world clinical practice in dermatology.