Which Pre-Treatments Best Prime Skin for Photodynamic Therapy
The skin’s optimal response to photodynamic therapy (PDT), used for treating actinic keratoses (AKs), is enhanced when skin is pretreated to facilitate local uptake of photosensitizing agents. Some moderate or thick AKs respond less to PDT, which is hypothesized to be due to a more limited penetration of photosensitizing agents and suboptimal protoporphyrin IX (PPIX) accumulation. Pretreating skin to remove crusts, scales and hyperkeratotic tissue has typically been done using curretage, but newer methods such as ablative fractional laser (AFXL), non-AFXL, microdermabrasion, and microneedling, have been gaining in popularity.
These methods impair the stratum corneum (SC) barrier and are thought to increase the uptake of the photosensitizer. A recent study sought to compare the various methods of skin pretreatment to determine which increased PPIX accumulation and the overall effect of PDT in healthy skin. Twelve healthy patients participated in this intraindividual, randomized clinical trial. In each participant, 17 test areas of 2 × 4 cm were mapped on the upper back and exposed to a panel of standardized physical interventions (curettage, microdermabrasion, microneedling, AFXL, and non-AFXL) plus untreated and methyl aminolevulinate–treated control areas. The primary outcome measure was PPIX fluorescence accumulation.
The results showed that AFXL, microdermabrasion, microneedling, and curettage all enhance PPIX accumulation and PDT reactions in normal skin. Pretreatment with AFXL ensured the highest and most homogeneous PPIX fluorescence, and a similar PPIX-enhancing potential was found for curettage, microdermabrasion, and microneedling.
The authors note that each pretreatment procedure is associated with advantages and disadvantages. For example, curettage and microneedling are operator dependent while AFXL requires access to costly laser equipment. Other limitations from this study include the use of healthy subjects which may limit the applicability of the results. However, this is the first study to provide head-to-head comparisons of the various methods.
Byline: Martha L. Sikes, MS, RPh, PA-C
Posted: May 31, 2017
Adapted from the original article.
[Image: DermNet New Zealand]