WAIKOLOA, HAWAII – Just because a dermatologist has photodynamic therapy equipment in the office doesn’t mean it should be applied to every skin condition that comes through the door, Dr. Jerome M. Garden cautioned at the Hawaii Dermatology Seminar sponsored by the Global Academy for Medical Education/Skin Disease Education Foundation.
"Used selectively, I think PDT can be truly worthwhile in some of our patients. But we run into problems when we decide it’s a cure-all for everything. Just because it’s available does not always make it the best choice around," said Dr. Garden, who is director of the Physicians Laser and Dermatology Institute as well as a professor of clinical dermatology and biomedical engineering at Northwestern University in Chicago.
Looking through the literature, it’s quickly apparent that PDT has been used to treat a bewildering array of dermatologic disorders, in most cases with less than stellar results.
"In my practice, I’m using PDT to treat just two things: actinic keratoses and actinic cheilitis, which is a close cousin. Why am I not using it to treat more disease processes? Because it has to be worth it. PDT is not simple to do. It takes a lot of your time and it costs you money. Insurance doesn’t necessarily help you with this. Either the patient’s insurance will reimburse you at an incredibly low rate, where it’s basically costing you money to do it, or you go outside of the insurance – and PDT is an expensive procedure," he noted.
The substantial time expenditure involved in PDT stems from the need to use microdermabrasion or another method of skin preparation to help the topical photosensitizing agent penetrate better. This is followed by an incubation time of 1-3 hours as the photosensitizer finds its target, and then light therapy to create the reactive oxygen species, which kills the targeted cells. The duration of light therapy is source dependent; blue light, for example, must be applied for 15-20 minutes.
PDT has other shortcomings in addition to the cost and time involved. It can be painful and entails several days of down time because of scaling and crusting. Plus, multiple treatment sessions are usually required, the dermatologist continued.
The 2012 American Society for Dermatologic Surgery member survey found that dermatologic surgeons performed roughly 205,000 PDT procedures during the year. The bulk was for actinic keratoses, acne, and rosacea.
"I didn’t even know until I saw this list that anybody treats rosacea with PDT," noted Dr. Garden. "A lot of people out there who are doing PDT use it for many more things than I do. But I’m just telling you what I do."
"I’ve tried it for acne. It helps, but depending on the light source, it can be a painful procedure. There’s a lot of desquamation afterward, and you have to go through it a few times. So you have to have a highly motivated patient – and even then, it doesn’t work all the time," he said.
Dr. Garden cited a Danish split-face study of pulsed-dye laser-assisted PDT vs. pulsed-dye laser therapy alone. Twelve weeks after completing three treatment sessions, the PDT side showed an 80% reduction in inflammatory acne lesions, compared with a 67% drop with pulsed-dye laser, and a 53% decrease in noninflammatory lesions compared to a 42% reduction with laser alone (J. Am. Acad. Dermatol. 2008; 58:387-94).
"Even without the topical photosensitizer, patients did pretty well," he commented.
As for PDT in cutaneous malignancies, Dr. Garden highlighted a recent literature review by dermatologists at the University of South Florida, Tampa, which concluded that the therapy is equivalent or superior to cryosurgery for actinic keratoses. The investigators also deemed PDT suitable for Bowen’s disease lesions provided they are large, widespread, or on difficult to treat areas, as well as for squamous cell carcinomas, but only when surgery is contraindicated. PDT may also provide better cosmetic outcomes than surgery or cryosurgery for superficial basal cell carcinomas (Dermatol. Surg. 2013;39:1733-44).
Dr. Garden called PDT his current first-line treatment for actinic cheilitis.
"I used to use the CO2 laser exclusively. It works very well, much better than PDT. But when I’d strip off the top layer of skin with the CO2 laser, patients would end up with an open wound that took a long time to heal. That’s hard for the patient to tolerate. And occasionally we’d see fibrosis of the lip. You don’t see that with PDT, although with PDT you usually need to do two or three treatments, and the area is red and swollen for 2-4 days. I like PDT. It’s my go-to therapy. When it fails, I turn on the CO2 laser," he said.