BJD

British Journal of Dermatology

C O N CI S E C O M M U N I C A T I ON

Light protection of the skin after photodynamic therapy reduces inflammation: an unblinded randomized controlled study B. Petersen, S.R. Wiegell and H.C. Wulf Department of Dermatological Research, Copenhagen University, D92, Bispebjerg Hospital, Bispebjerg Bakke 23, DK-2400 Copenhagen, Denmark

Summary Correspondence Bibi Petersen. E-mail: [email protected]

Accepted for publication 1 February 2014

Funding sources Galderma provided the foundation and sunscreen used in this study, but no other funding.

Conflicts of interest H.C.W. has received payment for lectures from Galderma. DOI 10.1111/bjd.12882

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 daylightactivated PpIX. Methods On the right arm of 15 subjects with sun-damaged skin, four identical squares (3 9 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.

What’s already known about this topic?

• •

The inflammatory response due to photodynamic therapy (PDT) is unavoidable. It has been shown that application of inorganic sunscreen containing 3
2% iron during PDT reduces blue-light sensitivity.

What does this study add?

• •

© 2014 British Association of Dermatologists

We demonstrated a continuous formation of protoporphyrin IX after PDT and a subsequent increased erythema when skin was illuminated with artificial daylight. Protection with inorganic sunscreen or foundation during illumination with artificial daylight after PDT reduced inflammation moderately, while protection with light-blocking plaster reduced the inflammation significantly.

British Journal of Dermatology (2014) 171, pp175–178

175

176 Light protection after PDT, B. Petersen et al.

Topical photodynamic therapy (PDT) with methyl aminolaevulinate (MAL) is commonly used in the treatment of actinic keratoses and nonmelanoma skin cancer.1 In the keratinocyte mitochondria, MAL is converted into the photosensitizer protoporphyrin (Pp)IX.2 During treatment PpIX is activated and degraded by illumination with red light, but after treatment there is a continued formation of PpIX due to an intracellular pool of MAL.3 Therefore exposure to daylight may increase the degree of post-treatment erythema. The side-effect of post-PDT exposure has not been examined, and the aim of this study was to investigate whether application of inorganic sunscreen, foundation or light-blocking plaster could reduce the inflammation caused by light exposure after PDT.

Materials and methods

Ochsenfurt, Germany). The slide projector gave 60 000 lx at a distance of 30 cm between lens and skin. The projector has an emission spectrum that can activate PpIX, but it emits less blue light than is present in natural daylight (Fig. 1). After illumination all squares were washed and covered from light exposure until the erythema measurements the following day. Objective measurement of erythema Erythema as an indicator of inflammation was measured objectively before and 24 h after treatment using a skin reflectance meter (UV Optimize Scientific 558; Chromo-Light, Espergaerde, Denmark).4 Zero percentage skin erythema is the reflectance from a blood-drained skin area, and 100% skin erythema is the reflectance from a highly vascular skin lesion such as that found in a dark blue facial naevus flammeus.5

Participants The participants were recruited and the study conducted from April to August 2012. The inclusion criteria were age > 18 years and sun-damaged skin on the dorsal aspect of the lower arm, defined as skin with multiple lentigines or/and guttate hypomelanosis. The exclusion criteria were pregnancy, breastfeeding, orally administered immunosuppressive medication within the last 3 months, porphyria, any sun sensitivity, or a known allergy to any of the constituents of the Metvix cream (MAL), sunscreen or foundation. Design and treatment The study was an unblinded randomized controlled study. Each participant had four squares of 3 9 3 cm marked on the skin of the dorsal aspect of the right lower arm. All squares had superficial curettage and conventional PDT. Metvixâ (160 mg g 1 MAL hydrochloride; Galderma, Lausanne, Switzerland) was applied with an approximately 0
5-mm-thick layer and then covered for 3 h with an opaque plaster, after which all the squares were illuminated with red light 37 J cm 2 in one field. Immediately after illumination the four squares were randomized to four different treatments, conducted as a 4-block randomization with closed envelopes created by a secretary (Fig. S1; see Supporting Information). Square 1: Uncovered (control). Square 2: Covered with approximately 2 mg cm 2 inorganic sun protection factor (SPF) 50 sunscreen containing titanium dioxide 11%, zinc oxide 2
4% and iron dioxide 0
2% (Av
ene 50 Cr
eme Minerale; Laboratoires Dermatologiques Av
ene, Boulogne, France). Square 3: Covered with approximately 2 mg cm 2 SPF50 foundation containing titanium dioxide 15%, zinc oxide 6
8% and iron dioxide 3
2% (Av
ene 50 Compact; Laboratoires Dermatologiques Av
ene). Square 4: Covered with light-blocking silver plaster (Advance, Leicester, U.K.). All skin squares were then illuminated for 2 h with artificial ‘daylight’ from a slide projector (Silent 2500; Kindermann, British Journal of Dermatology (2014) 171, pp175–178

Protoporphyrin IX fluorescence As a secondary outcome PpIX fluorescence was measured by a fluorescence camera (Medeikonos PDD⁄PDT; Medeikonos AB, Gothenburg, Sweden) before red-light illumination, after redlight illumination and after artificial daylight illumination. The excitation wavelengths were 365 nm and 405 nm and the illumination time was 2 s. The mean PpIX fluorescence was calculated from the images using a MatLab program (MatLab 7.2.0.232; MathWorks, Natick, MA, U.S.A.). The fluorescence in each image was calibrated using a fluorescence standard (Uranyl Standard; J&M Analytische Mess- und Regeltechnik GmbH, Aalen, Germany), as previously described.6 Statistics We needed a sample size of 12 participants to reach a significance level of 5% and a power of 80%, based on the assumption that the lowest difference of clinical importance in mean

Fig 1. The protoporphyrin (Pp)IX absorption spectrum, the spectrum of daylight at noon on a summer day in Denmark, and the emission spectrum for the artificial ‘daylight’ emitted by the slide projector. The emission spectrum of the projector is predominantly in the range of visible light. The spectra are all normalized. © 2014 British Association of Dermatologists

Light protection after PDT, B. Petersen et al. 177

measured erythema percentage was 20% with an SD of 25%. The within-subject distributions of interest were assessed graphically and tested for normality by the Kolmogorov–Smirnov test, and the paired t-test was used to analyse for changes in measured fluorescence or erythema on the four squares. Ethics All participants signed a consent form. The study was conducted in accordance with the guidelines for good clinical practice and the Declaration of Helsinki. The study was approved by the Committee for Biomedical Research Ethics in Denmark (H-4-2011-152) and by the Danish Medicines Agency (EudraCT number 2011-006012-31).

Results Eleven women and four men with a mean age of 52 years (range 37–65) were included and completed the study in accordance with the protocol. Table 1 shows changes in mean PpIX fluorescence and erythema during PDT and during artificial daylight illumination for the four squares. There was a statistically significant decrease in PpIX fluorescence after artificial daylight illumination, except on the square protected with light-blocking silver plaster, where we found a statistically nonsignificant increase in PpIX fluorescence (Table 1). We were surprised to find that the fluorescence decreases on the squares protected with foundation and sunscreen were greater than on the unprotected control square (P = 0
03 and P = 0
06, respectively). No difference was found in fluorescence decrease between protection with sunscreen and foundation (P = 0
9). The decrease in PpIX fluorescence during artificial daylight illumination on the unprotected control square constituted approximately 40% of the decrease in PpIX fluorescence during PDT [(453 + 215)/ 1701 = 0
39].

Figure 2 shows the increase in erythema percentage from baseline to 24 h after treatment. We considered square 1 with no cover to be a control (no protection) and found that protection with light-blocking silver plaster gave a 44% erythema reduction (P = 0
002). The sunscreen and the foundation caused erythema reduction of 19% and 27%, respectively (P = 0
29, P = 0
10). Assuming linearity between light dose and erythema, we found the daylight protective effects of sunscreen and foundation to be 44% and 62%, respectively.

Discussion Our results confirm that there is formation of PpIX after PDT, and that this is activated by exposure to artificial daylight. We found that the PpIX fluorescence decreased more on the squares protected with sunscreen and foundation than on the unprotected control square (Table 1). In theory the PpIX fluorescence decrease during artificial daylight illumination on the unprotected squares was expected to be greater than on the protected squares, but the sunscreen and foundation were hard to remove, and recall has obviously blurred the fluorescence measurements. We found that this ‘additional photodynamic treatment’ during artificial daylight illumination increased erythema (inflammation) and that only light-blocking silver plaster gave effective full protection. Due to more blue light in natural daylight (Fig. 1), we suspect the effect on inflammation to be greater in real life. Data from a previous study have demonstrated that during treatment with daylight PDT there is no increase in cure rate by prolonging daylight-mediated PDT for more than 2 h.7 The extra inflammation as a result of post-PDT daylight exposure is thus only a disadvantage, although the same has not been shown for conventional PDT. We consider it a strength of our study that erythema, our primary outcome, was measured objectively, which we

Table 1 Mean  SD of protoporphyrin (Pp)IX fluorescence and erythema before and just after photodynamic therapy (PDT) and after artificial daylight illumination, with significance at P < 0
05. The unit of PpIX fluorescence is arbitrary PDT Square Fluorescence 1: Control (no protection) 2: Sunscreen SPF50 3: Foundation SPF50 4: Silver plaster (light blocking) Erythema (%) 1: Control (no protection) 2: Sunscreen SPF50 3: Foundation SPF50 4: Silver plaster (light blocking)

Artificial daylight illumination

Before 9480 9404 9430 9161

After

   

21
4 21
8 21
9 21
0

1774 2231 1662 1844

   

3
9 4
3 4
3 4
5

Change

P-value

Aftera 7325  770 6991  1046 6997  937 7913  1023

453  320b 754  618b 764  640b 215  461

< 0
0001 0
0003 0
0004 0
09

   

11
9  7
8 9
6  6
1 8
7  6
6 6
7  4
8

< 0
0001 < 0
0001 0
0002 < 0
0001

7779 7745 7761 7698

   

904 974 958 976

1701  1165 1660  1446 1670  1004 1463  170

< 0
0001 0
001 < 0
0001 0
0003

29
1 30
7 30
7 30
2

   

7
3 6
8 6
0 7
3

NA NA NA NA

NA NA NA NA

33
3 31
4 30
6 27
7

Change

9
21 8
01 8
01 6
71

P-value

SPF, sun protection factor; NA, not applicable. aThe fluorescence was measured immediately after daylight illumination, whereas erythema was measured the day following the treatment. bThe PpIX fluorescence decrease in square 1 should theoretically be greater than that on the protected squares 2 and 3, but the sunscreen and foundation were hard to remove after the artificial daylight illumination, which could possibly blur measurements of fluorescence.

© 2014 British Association of Dermatologists

British Journal of Dermatology (2014) 171, pp175–178

178 Light protection after PDT, B. Petersen et al.

Measured erythema

Mean increase in erythema percentage

12 10 8 6 4

11·9 SD 7·8

9·6 SD 6·1

8·7 SD 6·6

6·7 SD 4·8

2 0

Control Sunscreen (no protection) SPF50

Foundation Silver plaster SPF50 (light blocking)

Fig 2. Mean increase in objectively measured erythema on the four different squares 24 h after photodynamic therapy treatment and illumination with artificial daylight. SPF, sun protection factor.

consider more precise than visual determination of erythema on a clinical scale,8 and it makes blinded assessment superfluous. It may be considered a limitation that we treated sundamaged skin that did not require treatment, but our study imitates PDT of field cancerization in patients with multiple precancerous lesions. In conclusion, our study shows that light protection after PDT with inorganic sunscreens has an erythema-reducing effect, but is not optimal to prevent activation of reaccumulated PpIX. The protection achieved by light-blocking silver plaster can in practice, except for the face, be realized by sunblocking clothes, or by daylight avoidance as recommended.

References 1 Kennedy JC, Pottier RH. Endogenous protoporphyrin IX, a clinically useful photosensitizer for photodynamic therapy. J Photochem Photobiol, B 1992; 14:275–92.

British Journal of Dermatology (2014) 171, pp175–178

2 Morton CA, McKenna KE, Rhodes LE. Guidelines for topical photodynamic therapy: update. Br J Dermatol 2008; 159:1245–66. 3 Angell-Petersen E, Christensen C, M€ uller CR, Warloe T. Phototoxic reaction and porphyrin fluorescence in skin after application of methyl aminolaevulinate. Br J Dermatol 2007; 156:301–7. 4 Wulf HC. Method and Apparatus for Determining an Individual’s Ability to Stand Exposure to Ultraviolet Radiation. US Patent 4 882 598, 21 November 1989. 5 Renhua N, Stender I-M, Henriksen M, Wulf HC. Autofluorescence of human skin is age-related after correction for skin pigmentation and redness. J Invest Dermatol 2001; 116:536–40. 6 Wiegell SR, Haedersdal M, Philipsen P et al. Continuous activation of PpIX by daylight is as effective as and less painful than conventional photodynamic therapy for actinic keratoses: a randomized, controlled, single-blinded study. Br J Dermatol 2008; 158:740–6. 7 Wiegell SR, Hædersdal M, Eriksen P, Wulf HC. Photodynamic therapy of actinic keratoses with 8% and 16% methyl aminolaevulinate and home-based daylight exposure: a double-blinded randomized clinical trial. Br J Dermatol 2009; 160:1308–14. 8 Bodekær M, Philipsen PA, Karlsmark T, Wulf HC. Good agreement between minimal erythema dose test reaction and objective measurements: an in vivo study of human skin. Photodermatol Photoimmunol Photomed 2013; 29:190–5.

Supporting Information Additional Supporting Information may be found in the online version of this article at the publisher’s website: Fig S1. Photographic illustration of treatment squares 1–4 on the dorsal aspect of the lower arm. Each participant had four squares of skin (1–4) marked on the lower arm. The four squares were then randomized to the four different treatments. This was done by choosing a sealed envelope containing the combination. The envelopes were sealed by a secretary and arranged in blocks of four envelopes with one of each combination in random sequence. So after four participants, one of each treatment combination had been given in a random sequence.

© 2014 British Association of Dermatologists