New Light on Actinic Keratosis: Using PDT to Eliminate A Bothersome Skin Condition

MNM | January 31, 2014 | Actinic Keratosis, Discoveries | No Comments

Actinic keratosis, or AK, is an irritating skin condition often referred to as solar keratosis because of its connection with chronic sun damage. The term keratosis refers to small yet obvious red, brown, or skin-colored patches that occur most commonly on the head, neck, forearms or hands. These patches can be itchy, burning, or stinging, and they’re usually rough in texture. Fair-haired, pale-skinned, light-eyed people are the individuals most often afflicted by AK. At the present time, tens of millions of people in Europe and the United States are affected by the condition and seek treatment from dermatologists and primary care physicians.

What makes AK a special concern is the fact that it can progress and transform into non-melanoma skin cancer. Some medical scientists even regard it as an early stage of cancer. In any case, the successful treatment of AK may offer an opportunity to cut short the development of such common skin cancers as basal cell carcinoma and squamous cell carcinoma.

Photodynamic therapy (PDT), which entails the activation of a photosensitizer using visible light, has received high marks as a treatment for AK because it can usually eliminate the disease without the need for surgery. The European Commission has recently issued a marketing authorization for the photosensitizer called for 5-aminolaevulinic acid (5-ALA or Ameluz), and this applies to the entire European Union. This decision was based on a favorable report by the Committee for Medicinal Products for Human Use, which recommended a marketing authorization for 5-ALA for treating mild to moderate AK on the face and scalp.

5-ALA is metabolized to protoporphyrin IX, a natural, photoactive compound that accumulates within the AK lesions. Protoporphyrin IX becomes activated upon exposure to red light of a suitable wavelength and energy. In the presence of oxygen, reactive oxygen species are generated, thereby damaging and ultimately destroying the AK cells. The main advantage of this light-based strategy is its ability to achieve the complete elimination of the AK lesions.

The Committee’s report notes that the 5-ALA gel should cover the lesions and approximately five millimeters of the surrounding area with a film about one millimeter thick. The entire area of treatment should then be illuminated with a red light source, either with a narrow spectrum around 630 nm and a recommended light dose of approximately 37 (measured in Joules per square centimeter), or a broader and continuous spectrum in the range between 570 and 670 nm, with a light dose between 75 and 200.

Other aspects of the report are as follows:

One session of PDT should be administered for either single or multiple lesions.
Non-responding or partially responding lesions should be retreated in a second session three months after the first treatment.

The most common side effects are photosensitivity reactions (e.g., irritation and itching) at the site of application. The detailed scientific assessment and product information are available on the EMA website (www.ema.europa.eu).

Another 2014 report on the benefits of PDT for this skin condition has focused on the different types of lasers and laser treatment protocols that may enhance the photodynamic effect, as reported in the February 2014 Australian Journal of Dermatology. For example, some researchers have proposed using a carbon dioxide laser pre-treatment before giving the photosensitizer, as this may shorten the amount of time needed between administering the 5-ALA and the red light treatment.

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Sources

Tzogani K, Straube M, Hoppe U, Kiely P, O’Dea G, Enzmann H, Salmon P, Salmonson T, Pignatti F. The European Medicines Agency approval of 5-aminolaevulinic acid (Ameluz) for the treatment of actinic keratosis of mild to moderate intensity on the face and scalp: Summary of the scientific assessment of the Committee for Medicinal Products for Human Use. J Dermatolog Treat. 2014 Oct;25(5):371-4.

Sebaratnam DF, Lim AC, Lowe PM, Goodman GJ, Bekhor P, Richards S. Lasers and laser-like devices: Part two. Australas J Dermatol. 2014 Feb;55(1):1-14. Epub 2013 Nov 11.

Jang YH, Lee DJ, Shin J, Kang HY, Lee ES, Kim YC. Photodynamic therapy with ablative carbon dioxide fractional laser in treatment of actinic keratosis. Ann Dermatol. 2013 Nov;25(4):417-22.