Daylight PDT with MAL - current data and practical recommendations of an expert panel

Daylight-PDT: everything under the sun

5-Aminolevulinic acid-based photodynamic therapy (ALA-PDT) was first implemented over three decades ago and has since been mainly part of clinical practice for the management of pre-cancerous and cancerous skin lesions. Photodynamic therapy relies on the combination of a photosensitizer, light and oxygen to cause photo-oxidative damage of cellular components. 5-Aminolevulinic acid (ALA) is a natural precursor of the heme biosynthetic pathway, which when exogenously administered leads to the accumulation of the photoactivatable protoporphyrin IX. Although, effective and providing excellent cosmetic outcomes, its use has been restricted by the burning, stinging, and prickling sensation associated with treatment, as well as cutaneous adverse reactions that may be induced. Despite intense research in the realm of drug delivery, pain moderation, and light delivery, a novel protocol design using sunlight has led to some of the best results in terms of treatment response and patient satisfaction. Daylight PDT is the protocol of choice for the management of treatment of multiple or confluent actinic keratoses (AK) skin lesions. This review aims to revisit the photophysical, physicochemical and biological characteristics of ALA-PDT, and the underlying mechanisms resulting in daylight PDT efficiency and limitations.

[Decision criteria and patient characteristics for patient-oriented treatment of field cancerization : Standardized algorithm for personalized treatment concepts]

Hintergrund

Aktinische Keratosen (AK) zeichnen sich durch einen chronischen Verlauf aus, und häufig ist ein ganzes Hautareal betroffen (Feldkanzerisierung). Die patientenindividuelle Abwägung therapiespezifischer Vor- und Nachteile einer feldgerichteten Therapie ist herausfordernd.

Fragestellung

Ziel der vorliegenden Arbeit war die Entwicklung und Evaluierung patientenorientierter Entscheidungskriterien, die sich für die pragmatische Einordnung einer AK-Feldtherapie im Behandlungsalltag bei Patienten mit besonderer Prädisposition zur Feldkanzerisierung eignen (Patiententyp 1 bis 3).

Material und Methoden

Die Entwicklung der Entscheidungskriterien und der Patiententypologie erfolgte im Rahmen eines nominalen bzw. strukturierten Multi-level-Gruppenprozesses. Anhand der patientenrelevanten Entscheidungskriterien, der verfügbaren Evidenz aus klinischen Studien und entlang der Patiententypologie wurde ein Bewertungsalgorithmus etabliert, und feldgerichtete AK-Therapieoptionen wurden systematisch evaluiert.

Ergebnisse

Als patientenrelevante Kriterien für die Therapieentscheidung wurden u. a. Effektivität, Sicherheit, Praktikabilität der Therapie, Adhärenz, Kosmetik, Patientenpräferenz und Komorbiditäten identifiziert und näher spezifiziert. In Bezug auf diese Entscheidungskriterien und Patiententypen, bei denen eine Feldtherapie vorrangig indiziert ist, erfüllte die photodynamische Therapie mit Tageslicht das therapiebezogene Anforderungsprofil in besonderem Maße.

Schlussfolgerung

Die Definition von patientenrelevanten und therapiebezogenen Entscheidungskriterien in der AK-Feldtherapie erlaubt eine strukturierte und gleichzeitig praxisorientierte Herangehensweise, um spezifische Therapieoptionen einzuordnen und individuelle Therapieentscheidungen herzuleiten.

Treatment of cutaneous basal cell carcinoma with combined laser extirpation and methyl aminolevulinic acid: five-year success rates

INTRODUCTION

Basal cell carcinoma is the most common cancer. Excisional surgery is associated with a high clearance rate, at the expense of significant functional and aesthetic morbidity, especially within the T-zone or for extensive lesions. We report five-year follow-up outcomes for carbon dioxide laser extirpation of cutaneous basal cell carcinoma, assisted by immediate methyl aminolevulinate photodynamic therapy and cost-benefit considerations.

MATERIALS AND METHODS

Retrospective cohort database analysis of adult patients with biopsy-proven primary cutaneous basal cell carcinoma, completing five years of follow-up. Direct per-lesion cost was compared with conventional wide local excision. Patients with morphoeic basal cell carcinoma were excluded.

RESULTS

Treated lesions were up to 1% total body surface area and up to 3.8mm (1.38 ± 0.695cm, mean ± standard deviation) in biopsy-proven depth. At the five-year follow-up mark, 93.6% of treated areas remained free of recurrence. Nodular basal cell carcinoma was the most common subtype (41.5%). A mean tumour depth greater than 2 ± 0.872mm was significantly associated with recurrence (Mann-Whitney, p = 0.0487). For a service delivered through the NHS at 2015 prices, we report a 43% saving, equating to a saving of £235 per basal cell carcinoma or a national annualised saving of £70 million by 2025 for the NHS.

CONCLUSION

Our results suggest that CO2-assisted photodynamic therapy is non-inferior to excision but may offer better functional and cosmetic preservation at a fraction of the direct like for like cost of operative surgery. Investigation of this method by randomised controlled methodology is warranted.

[Photodynamic therapy-trends and new developments]

Photodynamic therapy (PDT) is a licensed and established procedure for the treatment of actinic keratosis, basal cell carcinoma, and Bowen's disease, but there are several new and clinically relevant developments and trends. These concern on the one hand the main components of PDT, which are the photosensitizer and the light source. Furthermore, modifications and therapy combinations have been developed that lead to an improved therapeutic efficacy. An important aspect of field-directed PDT is also skin cancer prevention. Finally, PDT has been used successfully for nonlicensed indications including inflammatory diseases and skin rejuvenation. This article focuses on these new developments and on recent guideline recommendations.

Weather-informed Light-tissue Model-Based Dose Planning for Indoor Daylight Photodynamic Therapy

Daylight activation for photodynamic therapy (PDT) of skin lesions is now widely adopted in many countries as a less painful and equally effective treatment mechanism, as compared to red or blue light activation. However, seasonal daylight availability and transient weather conditions complicate light dose estimations. A method is presented for dose planning without placing a large burden on clinical staff, by limiting spectral measurements to a one-time site assessment, and then using automatically acquired weather reports to track transient conditions. The site assessment tools are used to identify appropriate treatment locations for the annual and daily variations in sunlight exposure for clinical center planning. The spectral information collected from the site assessment can then be integrated with real-time daily electronic weather data. It was shown that a directly measured light exposure has strong correlation (R² : 0.87) with both satellite cloud coverage data and UV index, suggesting that the automated weather indexes can be surrogates for daylight PDT optical dose. These updated inputs can be used in a dose-planning treatment model to estimate photodynamic dose at depth in tissue. A simple standardized method for estimating light dose during daylight-PDT could help improve intersite reproducibility while minimizing treatment times.

Daylight photodynamic therapy for field cancerization: lessons from molecular biology

Actinic keratoses (AKs) represent in-situ squamous cell carcinomas that potentially invade subepidermal structures and may metastasize. Until now, it is unpredictable to determine which AK lesions show this aggressive behavior. As AKs usually occur in large sun exposed areas, field-directed treatments have become the standard treatment regimen. Among these, conventional photodynamic therapy (cPDT) with 5-aminolaevulinic acid (ALA) or methyl-aminolevulinate (MAL) using red light is particularly effective in the treatment of AKs, but acceptance of the therapy is impaired by severe pain during treatment. Daylight PDT (dPDT) has demonstrated to be an equally effective alternative treatment option which is less painful. Recent attempts to determine the risk of AKs that demonstrate particular aggressive biological behavior by implementation of clinical and histological characteristics of AKs have not lead to conclusive results. Therefore, a look at the molecular biology of AKs could serve as a useful tool to develop a risk profiling for separation of those patients that are of particular risk to develop invasive tumor and, by this, to facilitate a more effective and adapted treatment option.

Photodynamic therapy for aesthetic-cosmetic indications

Photodynamic therapy (PDT) is a well-established, non-invasive treatment for a variety of dermatologic disorders, including actinic keratosis. Furthermore, PDT results in marked improvements in the signs of skin aging, although currently there are no standardized guidelines for PDT in skin rejuvenation. Two types of PDT are available: conventional-PDT (c-PDT) and the newly introduced daylight-PDT (DL-PDT). Both require a topical photosensitizer, a light source and oxygen, and both are comparable regarding safety and efficacy for treatment of photo-induced skin aging. Treatment is particularly effective for improvement of fine wrinkles, skin roughness, actinic elastosis and mottled hyperpigmentation. The most widely studied topical sensitizers used in PDT are 5-aminolevulinic acid (ALA) and methyl aminolevulinate (MAL). A range of pre-treatment procedures help improve skin absorption of the photosensitizer and lead to significantly improved efficacy. A variety of activating light sources can be used for c-PDT, while DL-PDT uses natural daylight, making it easier to treat larger areas of photodamaged skin. A major limitation of c-PDT is significant treatment-related pain, but DL-PDT has proved to be an almost pain-free procedure. Treatment duration is based on individual patient need but most patients receive 2 to 3 treatment cycles, with results fully evident 3-6 months post-treatment. PDT for aesthetic-cosmetic treatments has established its value in modern procedural dermatology as mono- or combination therapy. A major, unique advantage of PDT is that it is a non-invasive treatment that effectively rejuvenates photodamaged skin, while successfully treating a range of dermatologic conditions, including prevention and therapy of pre-cancerous actinic keratosis.

Quantifying the radiant exposure and effective dose in patients treated for actinic keratoses with topical photodynamic therapy using daylight and LED white light

Daylight photodynamic therapy (dl-PDT) is as effective as conventional PDT (c-PDT) for treating actinic keratoses but has the advantage of reducing patient discomfort significantly. Topical dl-PDT and white light-PDT (wl-PDT) differ from c-PDT by way of light sources and methodology. We measured the variables associated with light dose delivery to skin surface and influence of geometry using a radiometer, a spectral radiometer and an illuminance meter. The associated errors of the measurement methods were assessed. The spectral and spatial distribution of the radiant energy from the LED white light source was evaluated in order to define the maximum treatment area, setup and treatment protocol for wl-PDT. We compared the data with two red LED light sources we use for c-PDT. The calculated effective light dose is the product of the normalised absorption spectrum of the photosensitizer, protoporphyrin IX (PpIX), the irradiance spectrum and the treatment time. The effective light dose from daylight ranged from 3  ±  0.4 to 44  ±  6 J cm^-2due to varying weather conditions. The effective light dose for wl-PDT was reproducible for treatments but it varied across the treatment area between 4  ±  0.1 J cm^-2 at the edge and 9  ±  0.1 J cm^-2 centrally. The effective light dose for the red waveband (615-645 nm) was 0.42  ±  0.05 J cm^-2 on a clear day, 0.05  ±  0.01 J cm^-2 on an overcast day and 0.9  ±  0.01 J cm^-2 using the white light. This compares with 0.95  ±  0.01 and 0.84  ±  0.01 J cm^-2 for c-PDT devices. Estimated errors associated with indirect determination of daylight effective light dose were very significant, particularly for effective light doses less than 5 J cm^-2 (up to 83% for irradiance calculations). The primary source of error is in establishment of the relationship between irradiance or illuminance and effective dose. Use of the O'Mahoney model is recommended using a calibrated logging illuminance meter with the detector in the plane of the treatment area.