Introduction

The 67th annual meeting of the American Academy of Dermatology was held March 6-10, 2009 in San Francisco, California. There were numerous informative posters and presentations on photodynamic therapy. This brief synopsis provides an overview of selected presentations from the meeting.

Photodynamic Therapy for Acne…Ready for Prime Time?

Two presentations discussed photodynamic therapy (PDT) and its role in the treatment of acne. In Symposium S032, chaired by R. Rox Anderson, MD, Dr. Merete Haedersdal MD, PhD reviewed the evidence for the treatment of acne with PDT using various light sources in her presentation entitled, "PDT for Acne Vulgaris and Rosacea1". Dr. Amy Taub, MD, reviewed the evidence for various non-medical treatments of acne, including PDT, in her presentation entitled, "Procedural Treatments for Acne2".

The concept of PDT in dermatology involves the application of a photosensitizing agent such as 5-aminolevulinic acid (ALA) (Levulan® Kerastick®, DUSA Pharmaceuticals, Inc) or methyl aminolevulinate (MAL) (Metvix®, PhotoCureASA) followed by activation of the agent with a light source. Following application, ALA or MAL is taken up by cells and converted to protoporphyrin IX (PpIX), an efficient photosensitizer. A light source is then used to activate PpIX that leads to the production of oxygen radicals and subsequent cell death in the targeted tissue.3 Specifically, PDT’s suggested mechanisms of action in the treatment of acne include antibacterial activity against Propionibacterium acnes (P. acnes), selective damage to sebaceous glands, reduction in follicular obstruction of keratinocyte shedding, and decreases in secondary host response.4

Both physicians discussed recent trends in the treatment of acne, such as the movement away from medical treatments in favor of alternative medical technologies such as PDT. Reasons clinicians may change their treatment approach of acne include increasing failure of antibiotic therapy due to bacterial resistance and Methicillin-Resistant Staph Aureus, escalating patient and parental concerns over side effects from medications, and stricter regulations on prescriptions for isotretinoin. Both presenters had performed their own research and published reviews on this subject, which were reviewed along with other clinical evidence.

Dr. Haedersdal discussed a study by Wiegell et al. comparing the treatment effect and tolerability of MAL-PDT vs. ALA-PDT5 in the treatment of acne vulgaris. Twelve weeks after treatment with these agents, the investigators found a 59% decrease in inflammatory acne lesions from baseline with no significant differences in effectiveness between the two groups. Another study cited by Dr. Haedersdal was performed by Wiegell and Wulf and showed the effectiveness of MAL-PDT and red light in the treatment of inflammatory acne. Compared to no change in the placebo group, the MAL-PDT group had a 68% reduction in inflammatory acne lesions at 12 weeks. However, comedonal lesions were not improved, and 7 of 19 patients chose not to continue the study due to side effects that included severe pain during treatment.6 Dr. Haedersdal and colleagues studied the efficacy and safety of MAL-PDT with long-pulsed dye laser (LPDL) versus long-pulsed dye laser alone in the treatment of acne vulgaris. MAL-LPDL provided an 80% reduction in inflammatory acne lesions versus a 67% reduction of inflammatory lesions on LPDL-treated sides. MAL-LPDL treated patients had a non-significant but increased percentage of side effects, although MAL-LPDL was much better tolerated than red light7. The physicians felt this was an important finding that may translate into improved tolerability and excellent efficacy in clinical practice. A report of acne treated with pulsed dye laser and 20% 5-ALA demonstrated excellent tolerability and efficacy8.

Dr. Taub’s review of the literature suggested that either pulsed dye laser or intense pulsed light (IPL) may be the most effective light source for activation of a photosensitizing agent.9 In Dr. Taub’s trial of 22 patients with moderate to severe acne, patients were randomized to photoactivation with intense pulsed light (IPL), intense pulsed light with radiofrequency (ELOS), or blue light with 10% ALA-PDT photosensitizer and 30 minute incubation time. Median inflammatory lesion count reduction after 12 weeks and 3 treatments were 70% for IPL, 50% for ELOS and 30 % for blue light. Dr. Taub concluded that IPL was the most advantageous way to activate a photosensitizer for acne10. She also noted there were few issues regarding significant side effects. Both presenters agreed that issues still remain regarding PDT for acne and it might not be ready for mainstream use. Dr. Taub reiterated that she observed reliably good results with PDT and IPL, although many patients cannot afford the cost of treatment.

Dr. Taub questioned if PDT is a treatment modality best saved as last resort prior to isotretinoin, as many people end up with high deductible insurance plans. She also stated that she uses PDT preferentially for patients who wish to avoid oral medications or can’t take them for any reason.