PhotoSonx

Photodynamic therapy (PDT) relies on the interaction between a photosensitizer, the appropriate wavelength, and oxygen to cause cell death. First introduced about 100 years ago, PDT has continued to evolve in dermatology into a safe and effective treatment option for several dermatologic conditions. PDT is also used by pulmonologists, urologists, and ophthalmologists. This article focuses on the history of PDT, mechanism of action, photosensitizers and light sources used, therapeutic applications and expected dermatologic outcomes, as well as management of adverse events.

The therapeutic properties of light have been known for thousands of years, but it was only in the last century that photodynamic therapy (PDT) was developed. At present, PDT is being tested in the clinic for use in oncology--to treat cancers of the head and neck, brain, lung, pancreas, intraperitoneal cavity, breast, prostate and skin. How does PDT work, and how can it be used to treat cancer and other diseases?

Photodynamic therapy (PDT) employs a photosensitizer (PS) and visible light in the presence of oxygen, leading to production of cytotoxic reactive oxygen species, which can damage the cellular organelles and cause cell death. In dermatology, PDT has usually taken the form of topical application of a precursor in the heme biosynthesis pathway, called 5-aminolevulinic acid (or its methyl ester), so that an active PS, protoporphyrin IX accumulates in the skin. As PDT enhances dermal remodeling and resolves chronic inflamation, it has been used to treat cutaneous disorders include actinic keratoses, acne, viral warts, skin rejuvenation, psoriasis, localized scleroderma, some non-melanoma skin cancers and port-wine stains. Efforts are still needed to mitigate the side effects (principally pain) and improve the overall procedure.