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Updated: Mar 6, 2026
An In Vitro Approach to Photodynamic Therapy
Published on: August 17, 2018
Photodynamic Therapy Effectively Treats Actinic Keratoses Without Pre-Illumination Incubation Time
Abstract:
BACKGROUND: Actinic keratoses (AKs) are dysplastic lesions of the epidermis that have the potential to progress to non-melanoma skin cancers (NMSC). Traditional photodynamic therapy (PDT) requires a pre-illumination incubation time, which adds to overall in-office time and has been linked to pain. Our group has found a novel protocol to effectively treat AKs with PDT that eliminates the pre-illumination incubation period and uses 2 back-to-back cycles of 16 minute 40 seconds.
METHODS: The patient was prepped with soapy water and isopropyl alcohol, and thick AKs were descaled with a curette. Next, 5-aminolevulinic acid (ALA) was applied to the treatment areas and the patient was immediately placed under the blue light for 33 minutes and 20 seconds (two cycles of 16m/40s).
RESULTS: During therapy, the patient reported no pain. At one week, treated areas revealed a good reaction. The procedure was repeated at one month to treat residual AKs. At a 4-month follow-up, the patient's face and scalp showed near clearance of any AKs.
CONCLUSION: During PDT, the photosensitizer aminolevulinic acid (ALA), or in Europe methyl aminolevulinate (MAL), is utilized as a synthetic precursor that preferentially accumulates in dysplastic cells. The precursor then converts to PpIX via the heme pathway and causes apoptosis of the cells when excited, most commonly by either blue-violet (400-430 nm) or red (630-635 nm) light. Shorter incubation times are associated with reduced pain because less PpIX will have accumulated in the treated tissue by the start of the exposure to the light. The doubling of the light exposure time allows comparable levels of the photosensitizing molecule to accumulate and be activated so as to produce an equivalent reaction. The associated reduction in pain along with a more convenient treatment schedule makes this PDT protocol more tolerable and convenient to some patients.
J Drugs Dermatol. 2017;16(3):275-278.
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