A randomized, double-blind, placebo-controlled study of the efficacy of tetracaine gel (AmetopR) for pain relief during topical photodynamic therapy

Is a 4 J/cm2 PpIX-Weighted Simulated Daylight (SDL-PDT) Dose Still Efficient for Photodynamic Therapy of Actinic Keratosis?

Background: Several solutions are now proposed to provide indoor illumination with so-called artificial white light or simulated daylight (SDL-PDT), resulting in an effective treatment for actinic keratosis (AK). However, the optimal PpIX-weighted light dose is still debated. Integrating the effective irradiance over the irradiation time yields the effective light dose, which is also known as the protoporphyrin IX-weighted light dose and is a key parameter for the efficacy of the treatment. Objectives: The paper aims to report the clinical outcomes of SDL-PDT when using the PpIX-weighted light dose of 4 J/cm2, in patients treated for AK lesions of the scalp or the face at our medical dermatology center (ClinicalTrials.gov NCT052036). Methods: A total of 30 patients (16 males, 14 females), with a mean age of 71.0 ± 10.2, with phototype 1 (16 patients) and phototype 2 (14 patients) with grade I-II AK were treated with a drug light interval (DLI) of 10 min and a light exposure of 35 min (Dermaris, Surgiris, Croix, France), corresponding to a PpIX-weighted light dose of 4 J/cm2. The primary endpoint was the cure rate of patients at six months post-treatment. Secondary endpoints included scores of pain, erythema, crusts, and discomfort during or/and post the treatment. Results: In total, 762 AK were treated. Six months following treatment, the cure rate of the patients was 77%. The median pain score was less than 1 out of 10 for most of the patients. Erythema was observed in all patients and lasted 3 days (±1.5 day). Crusts were seen in 28 patients. Discomfort was reported as mild or less in more than 97% of patients. Conclusions: The shortening of the PpIX-weighted light dose to 4 J/cm2, corresponding to an illumination duration of 35 min with the Dermaris, does not modify the efficacy of the SDL-PDT. This observation is in agreement with recent published data demonstrating that the light dose can be reduced. Furthermore, this clinical study confirmed that SDL-PDT is an effective and nearly painless treatment with minimal side effects for patients with AK lesions of the scalp.

Advances in Photodynamic Therapy for the Treatment of Actinic Keratosis and Nonmelanoma Skin Cancer: A Narrative Review

Photodynamic therapy (PDT) with photosensitization using 5-aminolevulinic acid (ALA) [including a nanoemulsion (BF-200 ALA)] is approved in the USA for the treatment of actinic keratoses (AKs); another derivative, methyl aminolevulinate, is not approved in the USA but is used in Europe. For AK treatment, the photosensitizer may be applied to individual AK lesions or, depending on treatment regimen, to broader areas of sun-damaged skin to manage field cancerization, although not all products are approved for field treatment. ALA-PDT and photosensitizers have also been used off-label for the treatment of nonmelanoma skin cancers, primarily basal cell carcinomas (BCCs) and cutaneous squamous cell carcinomas (cSCC). Advantages of PDT include potentially improved cosmesis and patient satisfaction; disadvantages include pain and duration of treatment. Alternative illumination approaches, including intense pulsed light as well as pulsed-dye lasers, have also been used successfully. Pretreating the affected tissue or warming during incubation can help to increase photosensitizer absorption and improve therapeutic efficacy. Combinations of multiple treatments are also under exploration. Reducing incubation time between photosensitizer application and illumination may significantly reduce pain scores without affecting treatment efficacy. Substituting daylight PDT for a conventional illumination source can also reduce pain without compromising efficacy. The objective of this narrative review is to describe current and ongoing research in the use of topical photosensitizers and modified light delivery regimens to achieve improved therapeutic outcomes with less toxicity in patients with AK, cSCC, BCC, and field cancerization.

Dual wavelength 5-aminolevulinic acid photodynamic therapy using a novel flexible light-emitting diode unit

BACKGROUND

Photosensitizers used for photodynamic therapy (PDT) to treat dermatologic disease are metabolized into mainly protoporphyrin IX (PpIX), which has five absorption wavelength peaks: 410 nm, 510 nm, 545 nm, 580 nm, and 630 nm. Although only red light around 635 nm and blue light around 400 nm are used as light sources for PDT, the efficiency of PDT might be improved by using multiple wavelengths, including those that correspond to the other absorption peaks of PpIX. Furthermore, because the target disease often occurs on the face, a flexible-type light-source unit that can be fitted to the lesion without unnecessarily exposing the mucous membranes, e.g., the eyes, nostrils, and mouth, is preferred.

OBJECTIVE

We investigated the efficacy of a flexible light-emitting diode (LED) unit that emits multiple wavelengths to improve PDT effects.

METHODS

HaCaT cells were incubated with 5-ALA and subsequently irradiated with either a single wavelength or sequentially with two wavelengths. Cell viability and reactive oxygen species were analyzed. Nude mice were implanted with COLO679 cells by subcutaneous injection into the flank. 5-ALA was subcutaneously injected into the tumor. The tumor was irradiated with 50 J/cm² (day 0) and assessed daily until day 21.

RESULTS

The synergistic PDT effects of dual-wavelength irradiation and reactive oxygen species production were highest with the 405-nm and 505-nm wavelength combination. This dual wavelength combination was also the most effective in vivo.

CONCLUSION

We could therefore conclude that dual-wavelength PDT is an efficient strategy for improving the therapeutic effects of PDT. Using a flexible LED unit is expected to achieve more uniform irradiation of uneven areas.

A prospective, randomized, within-subject study of ALA-PDT for actinic keratoses using different irradiation regimes

BACKGROUND

Photodynamic therapy (PDT) can be used to treat large fields of actinic keratoses (AKs) with high clearance rates. A notable downside is the amount of pain that accompany the treatment. This study aimed to optimize the illumination protocol during conventional PDT in order to reduce pain without compromising treatment effectiveness.

METHODS

In this prospective, randomized study with a split-face design, patients with, symmetrically distributed AKs were included. All patients were treated using a ALA 78 mg/g gel. One side was illuminated with the Aktilite^® CL-128 lamp and the other side with the RhodoLED^® lamp in which the light intensity gradually increased to a maximum of 60%. Both sides received a total light dose of 37 J/cm² . Pain during the treatment was measured using a visual analogue scale. The clinical effectiveness of the 2 treated sides was assessed after 12 weeks.

RESULTS

Twenty-nine patients with 399 AKs were included. Illumination with the gradually increasing light intensity resulted in a decrease in the median visual analogue scale score by 1.1 points. Clearance rates were similar between the 2 lamps.

CONCLUSION

Minimizing the light intensity during the illumination phase of PDT reduces pain, while still preserving a high clearance rate of AKs.

Pain during topical photodynamic therapy - comparing methyl aminolevulinate (Metvix®) to aminolaevulinic acid (Ameluz®); an intra-individual clinical study

BACKGROUND

Actinic keratoses are often treated by photodynamic therapy. However, the main side effect of this treatment is pain during and shortly after illumination.

OBJECTIVES

To evaluate, in an intra-individual study, whether the pain response differ in treatment of actinic keratoses in scalp and forhead, using branded methyl aminolevulinate (MAL) and aminolaevulinic acid (ALA).

MATERIALS AND METHODS

Patients with mild to moderate actinic keratoses on forehead and scalp were treated with methyl aminolaevulinate (MAL)-PDT and aminolaevulinic acid (ALA)-PDT on two similar areas of forehead and scalp. The pain response were measured using visual analogue scale ranging from 0 to 10 during the illumination and 30min after the treatment.

RESULTS

Fourteen patients completed treatment to MAL and ALA-PDT. We found no significant difference in pain intensity between MAL and ALA-PDT, neither during the treatment (p-value=1) nor 30min after the treatment (p-value of 0.19).

CONCLUSIONS

This intra-individual study demonstrate no significant difference between the pain response during PDT using methyl aminolevulinate and aminolaevulinic acid.

In situ production of ROS in the skin by photodynamic therapy as a powerful tool in clinical dermatology

Photodynamic therapy (PDT) is a clinical modality of photochemotherapy based on the accumulation of a photosensitizer in target cells and subsequent irradiation of the tissue with light of adequate wavelength promoting reactive oxygen species (ROS) formation and cell death. PDT is used in several medical specialties as an organ-specific therapy for different entities. In this review we focus on the current dermatological procedure of PDT. In the most widely used PDT protocol in dermatology, ROS production occurs by accumulation of the endogenous photosensitizer protoporphyrin IX after treatment with the metabolic precursors 5-methylaminolevulinic acid (MAL) or 5-aminolevulinic acid (ALA). To date, current approved dermatological indications of PDT include actinic keratoses (AK), basal cell carcinoma (BCC) and in situ squamous cell carcinoma (SCC) also known as Bowen disease (BD). With regards to AKs, PDT can also treat the cancerization field carrying an oncogenic risk. In addition, an increasing number of pathologies, such as other skin cancers, infectious, inflammatory or pilosebaceous diseases are being considered as potentially treatable entities with PDT. Besides the known therapeutic properties of PDT, there is a modality used for skin rejuvenation and aesthetic purposes defined as photodynamic photorejuvenation. This technique enables the remodelling of collagen, which in turn prevents and treats photoaging stygmata. Finally we explore a new potential treatment field for PDT determined by the activation of follicular bulge stem cells caused by in situ ROS formation.

Photodynamic therapy--aspects of pain management

Topical photodynamic therapy (PDT) is a highly effective and safe treatment method for actinic keratoses with an excellent cosmetic outcome and is commonly used for the therapy of large areas of photodamaged skin with multiple clinically manifest and subclinical lesions. However, the major drawback of photodynamic therapy is the pain experienced during the treatment that can be intense and sometimes even intolerable for patients, requiring interruption or termination of the process. Several strategies for controlling pain during photodynamic therapy have been studied but few effective methods are currently available. Therefore, this review puts the spotlight on predictors on pain intensity and aspects of pain management during photodynamic therapy.

A prospective study of pain control by a 2-step irradiance schedule during topical photodynamic therapy of nonmelanoma skin cancer

BACKGROUND

Topical photodynamic therapy (PDT) for selected nonmelanoma skin cancer using 5-aminolevulinic acid (ALA) or methyl aminolevulinate (MAL) has yielded high long-term complete response rates with very good cosmesis. Pain during light activation of the photosensitizer can be a serious adverse event. A 2-step irradiance protocol has previously been shown to minimize ALA-PDT pain.

OBJECTIVE

To determine the irradiance-dependent pain threshold for MAL-PDT, to adapt the 2-step protocol to a light-emitting diode (LED) light source, and assess clinical response.

METHODS

In this prospective study, 25 superficial basal cell carcinoma (sBCC) received an initial irradiance by laser at 40 or 50 mW/cm², or LED at 35 mW/cm² followed by an irradiance at 70 mW/cm² for a total of 75 J/cm². Pain levels were recorded for both irradiance steps. Efficacy was assessed at 6, 12, or 24 months.

RESULTS

Pain was mild in the 40/70 mW/cm² laser cohort. Three instances of irradiance-limiting pain occurred at 50/70 mW/cm². Pain was minimal in the 35/70 mW/cm² LED cohort. Clinical response rates were 80% in the 50/70 mW/cm² laser cohort and 90% in the 35/70 mW/cm² LED cohort.

CONCLUSION

Topical PDT can be effectively delivered to sBCC with minimal treatment-related pain by a 2-step irradiance protocol.

Update on topical photodynamic therapy for skin cancer

Topical photodynamic therapy has become an established therapy option for superficial non-melanoma skin cancers with a substantial evidence base. In this update the increased choice in photosensitizers and light sources are reviewed as well as novel protocols to move beyond lesional treatment and address field therapy. Daylight PDT is emerging as an alternative to conventional office/hospital-based PDT that offers the advantage of much reduced pain. Although most studies have assessed efficacy of PDT in immune-competent patients, there is accumulating evidence for topical PDT being considered an option to assist in reducing the skin cancer burden in organ transplant recipients. The fluorescence associated with photosensitizer application can help delineate lesions prior to full treatment illumination and offers a useful adjunct to treatment in patients where diagnostic uncertainty or poor lesion outline complicates clinical care. PDT may also offer significant benefit in delaying/preventing new cancer development and combined with its recognized photo-rejuvenating effects, is emerging as an effective therapy capable of clearing certain superficial skin cancers, potentially preventing new lesions as well as facilitating photo-rejuvenating effects in treated areas.

Photodynamic therapy in dermatology: Dundee clinical and research experience

Topical photodynamic therapy (PDT) is increasingly accepted and used as a highly effective treatment for superficial non-melanoma skin cancer and dysplasia. We describe the developments in topical PDT for the treatment of skin diseases in our own PDT Centre in Dundee, both clinically and from a research base. Improvements in PDT could be achieved by optimisation of photosensitiser and light delivery, and these goals underpin the aims of our centre. We hope to facilitate the dissemination of use of PDT in dermatology throughout Scotland and outline some of the progress in these areas.

Ambulatory photodynamic therapy using low irradiance inorganic light-emitting diodes for the treatment of non-melanoma skin cancer: an open study

BACKGROUND/PURPOSE

Conventional photodynamic therapy (PDT) can be inconvenient and uncomfortable. We studied low irradiance PDT using an ambulatory inorganic light-emitting diode.

METHODS

Fifty-three patients with 61 lesions [superficial basal cell carcinoma (n = 30), Bowen's disease (n = 30), and actinic keratosis (AK; n = 1)] were studied. Two treatments of ambulatory PDT were undertaken 1 week apart (one treatment for AK). Clinical response was determined at 3 months, and the treatment cycle was repeated if there was residual disease. The endpoints assessed were pain during treatment (numerical rating scale (NRS); 0-10) and outcome at 1 year. Twenty-three of these patients also received conventional PDT to separate lesions.

RESULTS

The median NRS pain scores during first and second treatment were 2 (range 0-9) and 4 (0-9), respectively. Lesion clearance rate at 1 year after ambulatory PDT was 84% (21/25 lesions in 22 patients). Of the twenty-three patients treated with both ambulatory and conventional PDT, the median NRS was 1 (0-7) and 5 (1.5-9), respectively, with most patients preferring ambulatory PDT.

CONCLUSION

Ambulatory PDT is effective for superficial non-melanoma skin cancer, with 1 year clearance rates comparative to conventional PDT. Low irradiance ambulatory PDT may be less painful and more convenient than conventional PDT.

European guidelines for topical photodynamic therapy part 1: treatment delivery and current indications - actinic keratoses, Bowen's disease, basal cell carcinoma

Topical photodynamic therapy (PDT) is a widely used non-invasive treatment for certain non-melanoma skin cancers, permitting treatment of large and multiple lesions with excellent cosmesis. High efficacy is demonstrated for PDT using standardized protocols in non-hyperkeratotic actinic keratoses, Bowen's disease, superficial basal cell carcinomas (BCC) and in certain thin nodular BCC, with superiority of cosmetic outcome over conventional therapies. Recurrence rates following PDT are typically equivalent to existing therapies, although higher than surgery for nodular BCC. PDT is not recommended for invasive squamous cell carcinoma. Treatment is generally well tolerated, but tingling discomfort or pain is common during PDT. New studies identify patients most likely to experience discomfort and permit earlier adoption of pain-minimization strategies. Reduced discomfort has been observed with novel protocols including shorter photosensitizer application times and in daylight PDT for actinic keratoses.

Cutaneous penetration of the topically applied photosensitizer Pc 4 as detected by intravital 2-photon laser scanning microscopy

The fundamental mechanism of photodynamic therapy (PDT)-induced cell death has been characterized, but early critical PDT events in vivo remain incompletely defined. With the recent development in advanced fluorescence imaging modalities, such as intravital 2-photon laser scanning microscopy (2P-LSM), researchers are now able to investigate and visualize biological processes with high resolution in real time. This powerful imaging technology allows deep tissue visualization with single-cell resolution, thus providing dynamic information on the 3-dimensional architectural makeup of the tissue. The main goal of this study was to determine the cutaneous penetration of a topically applied photosensitizer, the silicon phthalocyanine Pc 4, into the skin of live animals and to assess the effective absorption of Pc 4 through the skin barrier. Our 2P-LSM images indicate that Pc 4 penetrates to the epidermal/dermal junction of mouse skin. The data also indicate that the degree of Pc 4 absorption is dose dependent. These findings represent initial steps that may help in improving the clinical utilization of topical Pc 4-PDT.

Pain in photodynamic therapy: mechanism of action and management strategies

Photodynamic therapy involves administration of a photosensitizing drug and its subsequent activation by irradiation with a light source at wavelengths matching the absorption spectrum of the photosensitizer. In many countries around the world, topical photodynamic therapy has been approved for treatment of cutaneous oncologic conditions such as actinic keratosis, Bowen's disease, and superficial basal cell carcinoma. Multicenter, randomized, controlled studies have confirmed its efficacy and superior cosmetic outcomes compared to conventional therapies. Nevertheless, this therapeutic method presents some adverse effects, such as erythema, edema, pigmentation, pustules, and pain. There is no doubt that pain is the most severe of the adverse effects, being sometimes responsible for definitive treatment interruption. The pain mechanism has not yet been fully understood, which makes complete pain control a challenge to be conquered. In spite of that, this literature review presents some useful pain management strategies as well as the most important pain-related factors in photodynamic therapy.

Successful cutaneous delivery of the photosensitizer silicon phthalocyanine 4 for photodynamic therapy

BACKGROUND

 Photodynamic therapy (PDT) has been shown to be effective in the treatment of malignancies of a variety of organ systems, including the lungs, bladder, gastrointestinal tract and skin. Cutaneous lesions serve as ideal targets of PDT because of the accessibility of the skin to light. To achieve optimum results, the photosensitizer must be delivered effectively into the target layers of the skin within a practical timeframe, via noninvasive methods.

AIM

To determine whether topical application of a second-generation photosensitizer, silicon phthalocyanine (Pc) 4 [SiPc(OSi(CH3)2 (CH2)3 N(CH3)2)(OH)], results in effective penetration of the skin barrier.

METHODS

Penetration of Pc 4 was evaluated using standard Franz-type vertical diffusion cell experiments on surrogate materials (silicone membranes) and laser-scanning confocal microscopy of normal skin biopsy samples from human volunteers.

RESULTS

The Franz diffusion data indicate that Pc 4 formulated in an ethanol/propylene glycol solution (70/30%, v/v) can penetrate the membrane at a flux that is appreciable and relatively invariant. Using the same formulation, Pc 4 uptake could be detected in human skin via laser-scanning confocal microscopy.

CONCLUSION

After topical application, Pc 4 is absorbed into the epidermis in as little as 1 h, and the absorption increased with increasing time and dose. Pc 4 can be effectively delivered into human skin via topical application. The data also suggest that the degree of penetration is time- and dose-dependent.

Recent advances in the prevention and treatment of skin cancer using photodynamic therapy

Photodynamic therapy (PDT) is a noninvasive procedure that involves a photosensitizing drug and its subsequent activation by light to produce reactive oxygen species that specifically destroy target cells. Recently, PDT has been widely used in treating non-melanoma skin malignancies, the most common cancer in the USA, with superior cosmetic outcomes compared with conventional therapies. The topical 'photosensitizers' commonly used are 5-aminolevulinic acid (ALA) and its esterified derivative methyl 5-aminolevulinate, which are precursors of the endogenous photosensitizer protoporphyrin IX. After treatment with ALA or methyl 5-aminolevulinate, protoporphyrin IX preferentially accumulates in the lesion area of various skin diseases, which allows not only PDT treatment but also fluorescence diagnosis with ALA-induced porphyrins. Susceptible lesions include various forms of non-melanoma skin cancer such as actinic keratosis, basal cell carcinoma and squamous cell carcinoma. The most recent and promising developments in PDT include the discovery of new photosensitizers, the exploitation of new drug delivery systems and the combination of other modalities, which will all contribute to increasing PDT therapeutic efficacy and improving outcome. This article summarizes the main principles of PDT and its current clinical use in the management of non-melanoma skin cancers, as well as recent developments and possible future research directions.

Pain during topical photodynamic therapy: uncomfortable and unpredictable

BACKGROUND

The major drawback of the widely used photodynamic therapy (PDT) is treatment-related pain.

OBJECTIVE

Gain insight into the intensity of and predictive factors for painful burning sensation associated with PDT.

METHODS

A prospective cohort study was performed at the department of Dermatology in the Maastricht University Medical Centre in Maastricht, a reference centre for dermatological oncology in The Netherlands. A total of 141 lesions in 108 patients were included, treated from November 2008 until June 2009 with PDT for superficial basal cell carcinoma, Bowen's disease (BD) or actinic keratosis (AK). Painful burning sensation was scored based on an 11-point pain intensity numeric rating scale (PI-NRS) (0=no pain; 10=worst possible pain).

RESULTS

The percentage of patients with a PI-NRS score over six was 32.6% and 37.9% during the primary and follow-up PDT session respectively. A total of 76.6% (95/124) of the patients was consistent in pain intensity score reporting. Factors associated with higher PI-NRS scores were treatment of AK or BD, tumour localization in the head/neck region, patient's age over 70, Fitzpatrick skintype I/II, photosensitizer 5-aminolevulinic acid and use of oral analgesics. After mutual adjustment of these factors, Fitzpatrick skintype remained the only independent predictor of PI-NRS scores during PDT.

CONCLUSION

It remains difficult to decide which patients should be considered for pain relieving measures. The solution remains to support all patients treated with PDT with pain relieving techniques or to let the support of pain relieving measures depend on the reported pain score for the primary session.

Simulations of measured photobleaching kinetics in human basal cell carcinomas suggest blood flow reductions during ALA-PDT

BACKGROUND AND OBJECTIVE

In a recently completed pilot clinical study at Roswell Park Cancer Institute, patients with superficial basal cell carcinoma (sBCC) received topical application of 20% 5-aminolevulinic acid (ALA) and were irradiated with 633 nm light at 10-150 mW cm(-2). Protoporphyrin IX (PpIX) photobleaching in the lesion and the adjacent perilesion normal margin was monitored by fluorescence spectroscopy. In most cases, the rate of bleaching slowed as treatment progressed, leaving a fraction of the PpIX unbleached despite sustained irradiation. To account for this feature, we hypothesized a decrease in blood flow during ALA-photodynamic therapy (PDT) that reduced the rate of oxygen transported to the tissue and therefore attenuated the photobleaching process. We have performed a detailed analysis of this hypothesis.

STUDY DESIGN/MATERIALS AND METHODS

We used a comprehensive, previously published mathematical model to simulate the effects of therapy-induced blood flow reduction on the measured PpIX photobleaching. This mathematical model of PDT in vivo incorporates a singlet-oxygen-mediated photobleaching mechanism, dynamic unloading of oxygen from hemoglobin, and provides for blood flow velocity changes. It permits simulation of the in vivo photobleaching of PpIX in this patient population over the full range of irradiances and fluences.

RESULTS

The results suggest that the physiological equivalent of discrete blood flow reductions is necessary to simulate successfully the features of the bleaching data over the entire treatment fluence regime. Furthermore, the magnitude of the blood flow changes in the normal tissue margin and lesion for a wide range of irradiances is consistent with a nitric-oxide-mediated mechanism of vasoconstriction.

CONCLUSION

A detailed numerical study using a comprehensive PDT dosimetry model is consistent with the hypothesis that the observed trends in the in vivo PpIX photobleaching data from patients may be explained on the basis of therapy-induced blood flow reductions at specific fluences.

An overview of topical photodynamic therapy in dermatology

This article is a review of the use of topical photodynamic therapy in dermatology and its current role in 2009 and future developments. The content of this article was presented at the EPPM in Wroclaw, September 2009.

Pain associated with aminolevulinic acid-photodynamic therapy of skin disease

BACKGROUND

Pain during topical aminolevulinic acid (ALA)-mediated photodynamic therapy (PDT) limits the use of this treatment of skin diseases.

OBJECTIVE

We sought to summarize the effectiveness of interventions to reduce ALA-PDT-related pain, and to explore factors contributing to pain induction.

METHODS

A PubMed search was performed to identify all clinical PDT trials (2000-2008) that used ALA or methyl-ALA, enrolled at least 10 patients per trial, and used a semiquantitative pain scale.

RESULTS

In all, 43 articles were identified for review. Pain intensity is associated with lesion size and location and can be severe for certain diagnoses, such as plaque-type psoriasis. Results are inconsistent for the correlation of pain with light source, wavelength of light, fluence rate, and total light dose. Cooling represents the best topical intervention.

LIMITATIONS

Pain perception differs widely between patients and can contribute to variability in the reported results.

CONCLUSION

Gamma-aminobutyric acid receptors, cold/menthol receptors (transient receptor potential cation channel, subfamily M, member 8), and vanilloid/capsaicin receptors (transient receptor potential cation channel, subfamily V, member 1) may be involved in pain perception during ALA-PDT and are therefore worthy of further investigation.

Guidelines for practical use of MAL-PDT in non-melanoma skin cancer

Methyl aminolaevulinate photodynamic therapy is increasingly practiced in the treatment of actinic keratoses, Bowen's disease and basal cell carcinomas. This method is particularly suitable for treating multiple lesions, field cancerization and lesions in areas where a good cosmetic outcome is of importance. Good treatment routines will contribute to a favourable result. The Norwegian photodynamic therapy (PDT) group consists of medical specialists with long and extensive PDT experience. With support in the literature, this group presents guidelines for the practical use of topical PDT in non-melanoma skin cancer.

Guidelines for topical photodynamic therapy: update

Multicentre randomized controlled studies now demonstrate high efficacy of topical photodynamic therapy (PDT) for actinic keratoses, Bowen's disease (BD) and superficial basal cell carcinoma (BCC), and efficacy in thin nodular BCC, while confirming the superiority of cosmetic outcome over standard therapies. Long-term follow-up studies are also now available, indicating that PDT has recurrence rates equivalent to other standard therapies in BD and superficial BCC, but with lower sustained efficacy than surgery in nodular BCC. In contrast, current evidence does not support the use of topical PDT for squamous cell carcinoma. PDT can reduce the number of new lesions developing in patients at high risk of skin cancer and may have a role as a preventive therapy. Case reports and small series attest to the potential of PDT in a wide range of inflammatory/infective dermatoses, although recent studies indicate insufficient evidence to support its use in psoriasis. There is an accumulating evidence base for the use of PDT in acne, while detailed study of an optimized protocol is still required. In addition to high-quality treatment site cosmesis, several studies observe improvements in aspects of photoageing. Management of treatment-related pain/discomfort is a challenge in a minority of patients, and the modality is otherwise well tolerated. Long-term studies provide reassurance over the safety of repeated use of PDT.

Irradiance-dependent photobleaching and pain in delta-aminolevulinic acid-photodynamic therapy of superficial basal cell carcinomas

PURPOSE

In superficial basal cell carcinomas treated with photodynamic therapy with topical delta-aminolevulinic acid, we examined effects of light irradiance on photodynamic efficiency and pain. The rate of singlet-oxygen production depends on the product of irradiance and photosensitizer and oxygen concentrations. High irradiance and/or photosensitizer levels cause inefficient treatment from oxygen depletion in preclinical models.

EXPERIMENTAL DESIGN

Self-sensitized photobleaching of protoporphyrin IX (PpIX) fluorescence was used as a surrogate metric for photodynamic dose. We developed instrumentation measuring fluorescence and reflectance from lesions and margins during treatment at 633 nm with various irradiances. When PpIX was 90% bleached, irradiance was increased to 150 mW/cm(2) until 200 J/cm(2) were delivered. Pain was monitored.

RESULTS

In 33 superficial basal cell carcinomas in 26 patients, photobleaching efficiency decreased with increasing irradiance above 20 mW/cm(2), consistent with oxygen depletion. Fluences bleaching PpIX fluorescence 80% (D80) were 5.7 +/- 1.6, 4.5 +/- 0.3, 7.5 +/- 0.8, 7.4 +/- 0.3, 12.4 +/- 0.3, and 28.7 +/- 7.1 J/cm(2), respectively, at 10, 20, 40, 50, 60 and 150 mW/cm(2). At 20-150 mW/cm(2), D80 doses required 2.5-3.5 min; times for the total 200 J/cm(2) were 22.2-25.3 min. No significant pain occurred up to 50 mW/cm(2); pain was not significant when irradiance then increased. Clinical responses were comparable to continuous 150 mW/cm(2) treatment.

CONCLUSIONS

Photodynamic therapy with topical delta-aminolevulinic acid using approximately 40 mW/cm(2) at 633 nm is photodynamically efficient with minimum pain. Once PpIX is largely photobleached, higher irradiances allow efficient, rapid delivery of additional light. Optimal fluence at a single low irradiance is yet to be determined.

Effect of (R)L-sulforaphane on 5-aminolevulinic acid-mediated photodynamic therapy

Topical photodynamic therapy (PDT) with 5-aminolevulinic acid (ALA), or so-called ALA-PDT, is a standard procedure in the clinical practice. For optimal treatment of nonmelanoma skin cancer, actinic keratoses and other dermatoses improvements are required because of adverse side effects, which include pruritus, erythema, edema, and pain. (R)L-sulforaphane (SF) is a compound that protects against erythema, but it can also induce DNA fragmentation that leads to cell death by apoptosis. The aim of our study was to investigate whether SF has any impact on protoporphyrin IX (PpIX) production and on PDT effectiveness. We have investigated some relevant properties of SF: its photostability in dimethyl sulfoxide (DMSO), its effect on ALA-induced production of PpIX in A431 human squamous carcinoma cells and in human skin, its effect on the photoinactivation of PpIX sensitized cells, and its effect on the rate of photobleaching of PpIX. SF had no influence on PpIX photodegradation, neither in solution nor in A431 cells. The synthesis of PpIX was increased by SF in human skin, but not in A431 cells. The average increase in PpIX fluorescence in human skin was 18% +/- 6% and 43% +/- 10% for ALA combined with 80 nmol/L SF and 120 nmol/L SF, respectively. Pretreatment with (R)L-sulforaphane before topical ALA-PDT may improve penetration of ALA through the stratum corneum, and, subsequently, increase PpIX synthesis.

Photodynamic therapy in dermatology--an update 2008

SUMMARY

Photodynamic therapy (PDT) is used for the prevention and treatment of non-melanoma skin cancer. Until recently, clinically approved indications have been restricted to actinic keratoses, nodular and superficial basal cell carcinoma, and--since 2006--Bowen disease. However, the range of indications has been expanding continuously. PDT is also used for the treatment of non-malignant conditions such as acne vulgaris and leishmaniasis, as well as for treating premature skin aging due to sun exposure. Here, PDT is used for the stimulation of immunomodulatory effects in contrast to the induction of necrosis and apoptosis as produced in the treatment of skin tumors. The porphyrin precursor 5-aminolevulinic acid (ALA) or its methyl ester (MAL, so far the only approved formulation in Europe) is applied topically as photosensitizer to exclude systemic reactions. Possible light sources include lasers as well as incoherent light sources; irradiation with incoherent light sources is cheaper and more appropriate for large treatment areas. The main advantages of PDT in comparison to other treatment modalities are its excellent cosmetic results and its high remission rates despite low invasiveness.This article provides up-to-date information about PDT with focus on recently published studies.