Weather conditions and daylight-mediated photodynamic therapy: protoporphyrin IX-weighted daylight doses measured in six geographical locations.

BACKGROUND: Photodynamic therapy (PDT) is an attractive therapy for nonmelanoma skin cancers and actinic keratoses (AKs). Daylight-mediated methyl aminolaevulinate PDT (daylight-PDT) is a simple and painless treatment procedure for PDT. All daylight-PDT studies have been performed in the Nordic countries. To be able to apply these results in other parts of the world we have to compare the daily protoporphyrin IX (PpIX) light dose in other countries with the PpIX light doses found in Nordic countries. OBJECTIVES: To calculate where and when daylight-PDT of AKs was possible in six different geographical locations using ground stations measuring PpIX-weighted daylight doses. METHODS: PpIX-weighted daylight doses were measured using a dosimeter with a customer-specific photodiode with a detector sensitivity that mimics the PpIX absorption spectrum and measures in 'PpIX doses'. The dosimeters were built into ground stations that were placed in six geographical locations measuring from July to December 2008. Temperature data for each location were obtained from the internet. The maximal ultraviolet (UV) index for Copenhagen was obtained for the measuring period of the dosimeters. RESULTS: If the PpIX light dose should be above 8Jcm(-2) and the maximum temperature of the day at least 10°C, it was possible to treat patients on nearly all days until the middle of September in Reykjavik and Oslo, until the last week of October in Copenhagen and Regensburg, until the middle of November in Turin and all year in Israel. CONCLUSIONS: Where and when to perform daylight-PDT depends on the PpIX light dose and outdoor temperature. The PpIX light dose was influenced by the geographical location (latitude), weather condition and time of year. The UV index was not more suitable than temperature and weather to predict if the intensity of daylight would be sufficient for daylight-PDT.

Daylight-mediated photodynamic therapy of moderate to thick actinic keratoses of the face and scalp: a randomized multicentre study.

BACKGROUND: Photodynamic therapy (PDT) is an attractive therapy for nonmelanoma skin cancers and actinic keratoses (AKs). Daylight-mediated PDT is a simple and tolerable treatment procedure for PDT. Methyl aminolaevulinate (MAL)-PDT is approved for the treatment of thin or nonhyperkeratotic AKs on the face and scalp. However, thick AK lesions are often treated as well when present in the field-cancerized treatment area. OBJECTIVES: In a randomized multicentre study to evaluate efficacy of daylight-mediated PDT for different severity grades of AKs. METHODS: One hundred and forty-five patients with a total of 2768 AKs (severity grades I-III) of the face and scalp were randomized to either 1½ or 2½ h exposure groups. After application of a sunscreen (sun protection factor 20) and gentle lesion preparation, MAL was applied to the entire treatment area. Patients left the clinic immediately after application and exposed themselves to daylight according to randomization. Daylight exposure was monitored with a wrist-borne dosimeter. RESULTS: No difference in lesion response was found between the 1½ and 2½ h exposure group. The mean lesion response rate was significantly higher in grade I lesions (75·9%) than in grade II (61·2%) and grade III (49·1%) lesions (P < 0·0001). Most grade II (86%) and III AKs (94%) were in complete response or reduced to a lower lesion grade at follow-up. Large variations in response rate of grade II and III AKs were found between centres. No association was found between response rate and light dose in patients who received an effective light dose of > 3·5 J cm(-2). CONCLUSIONS: Daylight-mediated PDT of moderate to thick AKs was less effective than daylight-mediated PDT of thin AKs especially in some centres. However, nearly all thicker lesions (grades II and III) were reduced to a lower lesion grade at 3 months after a single treatment of daylight-mediated PDT.

A randomized, multicentre study of directed daylight exposure times of 1½ vs. 2½ h in daylight-mediated photodynamic therapy with methyl aminolaevulinate in patients with multiple thin actinic keratoses of the face and scalp.

BACKGROUND: Actinic keratoses (AKs) are common dysplastic skin lesions that may differentiate into invasive squamous cell carcinomas. Although a superior cosmetic outcome of photodynamic therapy (PDT) is advantageous compared with equally effective treatments such as cryotherapy and curettage, the inconvenience of clinic attendance and discomfort during therapy are significant drawbacks. Daylight-mediated PDT could potentially reduce these and may serve as an alternative to conventional PDT. OBJECTIVES: To compare the efficacy of methyl aminolaevulinate (MAL)-PDT with 1½ vs. 2½ h of daylight exposure in a randomized multicentre study. METHODS: One hundred and twenty patients with a total of 1572 thin AKs of the face and scalp were randomized to either 1½- or 2½-h exposure groups. After gentle lesion preparation and application of a sunscreen of sun protection factor 20, MAL was applied to the entire treatment area. Immediately after, patients left the clinic and exposed themselves to daylight according to the randomization. Daylight exposure was monitored with a wristwatch dosimeter and patients scored their pain sensation during treatment. RESULTS: The mean lesion response rate at 3 months was 77% in the 1½-h group and 75% in the 2½-h group (P = 0·57). The mean duration of daylight exposure was 131 and 187 min in the two groups. The mean overall effective light dose was 9·4 J cm(-2) (range 0·2-28·3). Response rate was not associated with effective daylight dose, exposure duration, treatment centre, time of day or time of year during which the treatment was performed. Treatment was well tolerated, with a mean ± SD maximal pain score of 1·3 ± 1·5. CONCLUSIONS: Daylight-mediated MAL-PDT is an effective, convenient and nearly pain-free treatment for patients with multiple thin AKs. Daylight-mediated PDT procedures were easily performed and 2 h of daylight exposure resulted in uniformly high response rates when conducted in the period from June to October in Nordic countries.