Light Protection of the Skin After Photodynamic Therapy Reduces Inflammation

B Petersen, SR Wiegell, HC Wulf

B Petersen, SR Wiegell, HC Wulf
Light Protection of the Skin After Photodynamic Therapy Reduces Inflammation: An Unblinded Randomized Controlled Study
Br J Dermatol 2014 Jul 01;171(1)175-178

Protezione solareABSTRACT

BACKGROUND
Photodynamic therapy (PDT) is followed by significant inflammation. Protoporphyrin (Pp)IX is still formed in the skin after PDT and patients are sensitive to daylight 24-48 h after treatment. Exposure to daylight after PDT may therefore increase inflammation.

OBJECTIVES
To investigate whether protection with inorganic sunscreen, foundation or light-blocking plaster after PDT can reduce inflammation caused by daylight-activated PpIX.

METHODS
On the right arm of 15 subjects with sun-damaged skin, four identical squares (3 × 3 cm) were given conventional PDT treatment. Immediately after red-light illumination the squares were either left unprotected or protected by inorganic sunscreen [sun protection factor (SPF) 50], foundation (SPF50) or light-blocking plaster. The skin was then illuminated with artificial daylight for 2 h and afterwards covered for 24 h. Fluorescence and erythema (inflammation) were measured with a fluorescence camera and a reflectance meter.

RESULTS
PpIX was significantly reduced after artificial daylight illumination (P < 0·0004), except on the square protected with light-blocking silver plaster, where it had increased (P = 0·09). The increased erythema 24 h after treatment was reduced by 19% with the sunscreen (P = 0·29), by 27% with the foundation (P = 0·10) and by 44% with the silver plaster (P = 0·002).

CONCLUSIONS
Artificial daylight exposure after conventional PDT increases skin erythema. Light-blocking plaster gives more effective protection against post-PDT daylight exposure than inorganic sunscreen and foundation. In practice such full protection can be achieved by use of sun-blocking clothes or daylight avoidance for 24 h.

EXPERT COMMENT
Alexandra Zhang MD

Photodynamic therapy (PDT) is an effective modality for field treatment of actinic keratoses and certain non-melanoma skin cancers. Photosensitivity and pain are the most common complaints associated with PDT. Side effects are more severe in patients with severe actinic damage and in patients who are exposed to sunlight in the 24 hours after treatment.
The current study demonstrated superior efficacy of light-blocking plaster in reducing erythema and inflammation caused by light exposure after PDT compared with inorganic sunscreen and foundation (SPF 50). Most of us have been doing a good job in emphasizing the importance of sunscreen application in PDT patients. Given the evidence provided in the article, daylight protection using sun-blocking clothes or daylight avoidance should reduce inflammation, minimizing pain and discomfort in our patients.