Photodynamic therapy matures as treatment for superficial skin lesions

Hospitals and clinics worldwide use photodynamic therapy to treat skin lesions encountered in patients with superficial basal cell carcinoma, Bowen’s disease and actinic keratosis. At the Scottish PDT Centre — part of the University of Dundee and Ninewells Hospital & Medical School, both in Dundee, UK — staff have carried out several thousand such treatments.

In a review of the clinical and research applications of photodynamic therapy, Dr. Harry Moseley and his colleagues at the center and at the University of Texas at San Antonio focus on the results gleaned from the clinical practice in Dundee. The center has conducted more than 3400 treatments on more than 760 patients.

From a clinical angle, the authors describe the Scottish PDT Centre’s operational model; the light sources that they have used to conduct photodynamic therapy, including lasers and LEDs; and treatment methods, dosimetry issues, optimal fluence, pain management and phototoxicity, and clinical outcomes. From a research angle, they discuss interactions among proteins and photosensitizers, including those between protoporphyrin IX and small globular proteins, and the potential damage to nuclear DNA caused by therapy.

Overall, they report, topical applications of photodynamic therapy are easily performed by trained staff on an outpatient basis, and the treatments are generally well-tolerated, although pain can be a limiting factor. Some photosensitizers, including hypericin and Photofrin (porfimer sodium), made by Axcan Pharma Inc. of Birmingham, Ala., apparently cause DNA strand breaks; however, they have found no evidence that clinical photodynamic therapy is significantly mutagenic. They conclude that it is very suitable for treatment of such skin diseases as superficial basal cell carcinoma, Bowen’s disease and actinic keratosis.

The authors note that, despite the clinical success obtained thus far with photodynamic therapy, improving dosimetry should lead to even better outcomes. (Lasers in Surgery and Medicine, June 2006, pp. 403-416.)