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Applications: Can Photodynamic Therapy Stop Aging?

Photonics Spectra
Jan 2009
Gary Boas, gboas@eggship-media.com

Photodynamic therapy (PDT) is widely used for the prevention and treatment of nonmelanoma skin cancer. The primary indications for the technique thus far have been actinic keratoses, nodular and superficial basal cell carcinoma and, more recently, Bowen’s disease. Indeed, until a few years ago, it seemed that application of PDT might not extend beyond these.

A funny thing happened on the way to the clinic, though. “People figured out that, after treatment for sun damage – where a typical feature is the development of actinic keratoses – the skin became much softer, and dyspigmentation disappeared,” said Dr. Rolf-Markus Szeimies, a dermatologist and an investigator at the University of Regensburg in Germany. Fine wrinkles disappeared as well, leading researchers to coin the term “photorejuvenation” (sometimes “chemorejuvenation”) and to begin developing PDT for cosmetic as well as clinical use.

MDpdt_TX.jpg

Resarchers have found that treating nonmelanoma skin cancers with photodynamic therapy also results in reduction in dyspigmentation and wrinkles, leading them to coin the term “photorejuvenation” and to develop the technique for cosmetic applications. Shown here are images of a 64-year-old patient with multiple actinic keratoses on his forehead (left). Three months after treatment with photodynamic therapy (right), the actinic keratoses had disappeared, and the cosmetic appearance of the skin had improved significantly, with less erythema and dyspigmentation.


PDT is a noninvasive treatment that uses a photosensitizer or a photosensitizing agent called aminolevulinic acid (ALA), or its methyl ester MAL, which is applied to the skin and then activated by exposure to light. This topical administration allows dermatologists to treat specific areas of the skin without damaging any of the surrounding areas.

A number of studies have shown the potential of using PDT for cosmetic applications. In a 2006 Dermatologic Surgery paper, for example, Dr. Michael Gold and coworkers compared results from treatment using PDT with those from treatment using intense pulsed light alone. The study showed that crow’s-feet and rough areas of the skin improved by 55 percent in PDT patients, in contrast with 29.5 percent in patients who received only intense pulsed light treatment. At the same time, hyperpigmentation improved by up to 60 percent (as compared with 37.2 percent) and telangiectasias – small, dilated vessels that appear most commonly around the nose, cheeks or chin – by up to 84.6 percent (as compared with 53.8 percent).

Today, photodynamic therapy plays an important role in a booming cosmetic therapy industry. Antiaging and wellness centers across the nation now offer PDT sessions to tackle sun damage, fine lines and blotchy pigmentation. And the number of centers providing such services likely will only increase in coming years, especially as the US population continues to age.

Szeimies noted that these applications – and photodynamic therapy in general – will benefit from another recent development: use of different light sources. Conventional PDT uses either incoherent broadband lamps or continuous-wave lasers, which have proved uncomfortable for patients because of the long exposure times. Researchers have in the past several years shown the potential of sources such as flashlamps and pulsed dye lasers. Studies indicate that these are roughly as effective as the conventional sources but, because of the considerably reduced exposure times, significantly less painful. Thus patients likely will be more compliant during the procedures, and the procedures will be more effective than in the past.



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