Photodynamic therapy of non-melanoma malignant tumours of the skin using topical delta-amino levulinic acid sensitization and laser irradiation

Basal cell carcinoma: treatment options and prognosis, a scientific approach to a common malignancy

The incidence of basal cell carcinoma is rapidly increasing and a number of treatment modalities are available. Treatment of basal cell carcinoma includes both surgical and nonsurgical approaches, some of which are traditional, and others experimental. The treatment modality utilized is dependent on both the tumor type and the patient. In order to choose between therapies, evidence-based research is necessary. In an extensive review of the literature concerning treatment options for patients with basal cell carcinoma, we found that there are a limited number of comparative, prospective, randomized, long-term follow-up studies. Based on the results of the available studies, surgical excision, Mohs surgery and cryosurgery are the three standard therapies of choice. Other treatment modalities should be considered secondary choices. There are also promising new treatment options, such as photodynamic therapy, which need further investigation. Special attention is needed when treating the more aggressive subtypes of the disease, such as the micronodular, infiltrative, adenoid and morpheic forms of basal cell carcinoma, as well as bigger basal cell carcinomas and basal cell carcinoma recurrences.

In vivo pharmacokinetics of 8-aminolevulinic acid-induced protoporphyrin IX during pre- and post-photodynamic therapy in 7,12-dimethylbenz(a)nthracene-treated skin carcinogenesis in Swiss mice: a comparison by three-compartment model

Delta-aminolevulinic acid-photodynamic therapy (ALA-PDT) has emerged as a useful technique in the treatment of superficial basal cell carcinoma, actinic keratosis, squamous cell carcinoma and tumors of other organs. Earlier reports mention that there is reappearance of protoporphyrin IX (PpIX) after photoirradiation of tumors. This property of reappearance of PpIX is being utilized to treat nodular tumors by fractionated light dose delivery. However, there is still no unanimously accepted reason for this reappearance phenomenon and the rate of resynthesis after PDT. On account of this, studies are carried out on the estimation of the pharmacokinetics of the ALA-induced PpIX in mice tumor models and the surrounding normal tissues before and after PDT. Further, a mathematical model based on a multiple compartment system is proposed to estimate the rate parameter for the diffusion of PpIX from the surrounding normal tissues into the tumor tissue (km) caused by photobleaching during PDT with irradiating fluences of 36.0 and 57.6 J/cm2. The km value at two different fluences, 36.0 and 57.6 J/cm2, are estimated as 3.0636+/-0.7083 h(-1) and 6.9231+/-2.17651 h(-1), respectively. Further, the rate parameter for the cleavage and efflux of ALA (k1) and the rate parameter for the evasion of PpIX from the tumor tissues after PDT (kt) were also estimated by fitting the experimental data to the developed mathematical model. The statistical significance of the estimated parameters was determined using Student's t-test. The experimental results and the rate parameters obtained using the proposed compartment model suggest that in addition to the earlier reported reasons, the invasion or diffusion of PpIX from the surrounding tissues to the tumor tissues after photoirradiation might also contribute to the reappearance of PpIX after PDT.

Comparative permeation studies for delta-aminolevulinic acid and its n-butylester through stratum corneum and artificial skin constructs

The improvement of the permeation properties through excised human stratum corneum and artificial skin constructs (ASC) of delta-aminolevulinic-n-butylester (ABE) compared with delta-aminolevulinic acid (ALA) was investigated. For this purpose the permeated amounts of each substance were determined depending on time in a Franz diffusion cell experiment with stratum corneum and ASC, respectively. Furthermore the barrier properties of ASC were compared with those of stratum corneum. Detection of both substances was performed by high-performance liquid chromatography (HPLC) analysis. For the determination of ABE a new HPLC method was developed. ABE could be determined with the new HPLC method with sufficient sensitivity (detection limit: 0.1 microg/ml) after derivatisation with o-phthalaldehyde (OPA). Stratum corneum and ASC were more permeable for ABE than for ALA. The permeation coefficient P of ABE through stratum corneum was nearly ten-fold higher than that of ALA. Using ASC as permeation barrier the permeation coefficient of ABE was about 22-fold higher than that of ALA. ABE and ALA permeated 142-fold and 64-fold, respectively, faster through ASC than through stratum corneum.

In vitro/in vivo correlations between transdermal delivery of 5-aminolaevulinic acid and cutaneous protoporphyrin IX accumulation and effect of formulation

BACKGROUND

Photodynamic therapy (PDT) using topical application of 5-aminolaevulinic acid (ALA) has been widely reported for the treatment of a variety of neoplastic and non-neoplastic cutaneous diseases. Although different formulations containing variable amounts of ALA have been applied in PDT, the dose-response relationships between transdermal ALA delivery and cutaneous protoporphyrin IX (PpIX) accumulation have not been studied.

OBJECTIVES AND METHODS

The objectives of this study were to investigate the effect of permeability barrier function, ALA concentration and formulation on the in vitro penetration of ALA through nude mouse skin and cutaneous PpIX formation at 2 h following a 2-h application of ALA to nude mouse skin in vivo, and to delineate the relationships in between.

RESULTS

Results demonstrated that variations in barrier integrity, in addition to ALA concentration, profoundly influenced ALA delivery to generate PpIX. Saturable correlations were found to exist between PpIX concentrations in both the epidermis and dermis in vivo and its transdermal flux in vitro, and the relationships were well described by the Emax model. The established correlations based on pure aqueous solutions were applicable to different formulations containing hydroxypropylmethylcellulose as the gelling agent and ethylenediamine tetraacetic acid as the iron chelator. Moreover, incorporation of desferrioxamine, another iron chelator, in the formulation prolonged cutaneous PpIX accumulation in the skin in comparison with 3% ALA aqueous solution, but the peak PpIX levels were not increased. Application of a liposomal formulation resulted in similar prolongation in ALA-induced PpIX accumulation, as well as better epidermal targeting.

CONCLUSIONS

Knowledge of the dose-response relationships and the effect of formulation is important for designing optimal formulations and treatment schedules for topical ALA-PDT.

Guidelines for topical photodynamic therapy: report of a workshop of the British Photodermatology Group

Topical photodynamic therapy (PDT) is effective in the treatment of certain non-melanoma skin cancers and is under evaluation in other dermatoses. Its development has been enhanced by a low rate of adverse events and good cosmesis. 5-Aminolaevulinic acid (ALA) is the main agent used, converted within cells into the photosensitizer protoporphyrin IX, with surface illumination then triggering the photodynamic reaction. Despite the relative simplicity of the technique, accurate dosimetry in PDT is complicated by multiple variables in drug formulation, delivery and duration of application, in addition to light-specific parameters. Several non-coherent and coherent light sources are effective in PDT. Optimal disease-specific irradiance, wavelength and total dose characteristics have yet to be established, and are compounded by difficulties comparing light sources. The carcinogenic risk of ALA-PDT appears to be low. Current evidence indicates topical PDT to be effective in actinic keratoses on the face and scalp, Bowen's disease and superficial basal cell carcinomas (BCCs). PDT may prove advantageous where size, site or number of lesions limits the efficacy and/or acceptability of conventional therapies. Topical ALA-PDT alone is a relatively poor option for both nodular BCCs and squamous cell carcinomas. Experience of the modality in other skin diseases remains limited; areas where there is potential benefit include viral warts, acne, psoriasis and cutaneous T-cell lymphoma. A recent British Photodermatology Group workshop considered published evidence on topical PDT in order to establish guidelines to promote the efficacy and safety of this increasingly practised treatment modality.

Feasibility study of a system for combined light dosimetry and interstitial photodynamic treatment of massive tumors

A system for the photodynamic laser treatment of massive tumors that employs multiple optical fibers to be inserted into the tumor mass is described. The light flux through the tumor can be assessed by use of the individual fibers both as transmitters and as receivers. With a computer model that describes the diffusive light propagation, optical dosimetry is under development. The system has been tested in an experimental animal tumor model in preparation for clinical work. Currently, delta-aminolevulinic acid is used as a sensitizer, activated by 635-nm radiation from a 2.0-W compact diode laser system. With the availability of future, highly selective drugs absorbing approximately 750 nm, larger tumor volumes should be treatable, and surrounding, sensitive normal tissue should be spared.

PpIX fluorescence kinetics and increased skin damage after intracutaneous injection of 5-aminolevulinic acid and repeated illumination

Photodynamic therapy with topically applied 5-aminolevulinic acid is used successfully for superficial skin lesions. The results for thicker, nodular lesions are less favorable. The method of aminolevulinic acid administration, the concentrations of aminolevulinic acid, and the irradiation schemes used so far have not been investigated thoroughly. As aminolevulinic acid photodynamic therapy has high potential for the increasing problem of skin cancer, we investigated both visually and histopathologically the photodynamic-therapy-induced skin damage after intracutaneous administration of aminolevulinic acid in normal porcine skin. We also investigated the kinetics of the aminolevulinic-acid-induced photosensitizer protoporphyrin IX fluorescence after irradiation in relation to fluence and irradiance. Finally we investigated the effect on photodynamic-therapy-induced damage of a fractionated irradiation. This study demonstrates that intracutaneous administration of aminolevulinic acid leads to higher fluorescence levels and thus to formation of higher protoporphyrin IX concentrations than topical application of aminolevulinic acid cream. The peak level of protoporphyrin IX after intracutaneous administration of aminolevulinic acid is reached earlier than after topical administration. The comeback of fluorescence, indicating re-synthesis of protoporphyrin IX after irradiation, is inhibited with increasing fluence. Photodynamic-therapy-induced damage increases with increasing fluence, but is independent of the irradiance. Finally, the photodynamic-therapy-induced skin damage seems to be greater after fractionated irradiations with two equal light fractions of 15 J per cm2 separated by a dark interval of 2 h.

Topical 5-aminolaevulinic acid photodynamic therapy for the treatment of skin conditions other than non-melanoma skin cancer

Topical 5-aminolaevulinic acid (ALA) photodynamic therapy (PDT) is used increasingly for superficial non-melanoma skin cancer (NMSC) and dysplasia. However, the relative accumulation of the photosensitizer protoporphyrin IX (PpIX) in diseased tissue is not specific for neoplastic disease, and has been shown after the application of ALA to benign proliferative skin conditions such as viral warts and psoriasis. This review appraises the quality of evidence available for the use of topical ALA-PDT in the treatment of skin conditions other than NMSC. The diseases that have been studied in most detail are recalcitrant viral warts, acne, psoriasis and cutaneous T-cell lymphoma. Publications relating to the treatment of other diseases by topical PDT are restricted to small case series or case reports. The relevant literature will be discussed and the potential for topical PDT in the treatment of several skin diseases is highlighted, although more detailed studies are required to clarify the role of PDT beyond the treatment of NMSC.

Role of lasers and photodynamic therapy in the treatment of cutaneous malignancy

Tumor therapy is not a common indication for the use of lasers, as it is in the treatment of benign vascular skin lesions, since many alternative treatment modalities exist. However, certain patients may benefit from laser therapy of premalignant and malignant skin tumors. Skin tumors can be treated by laser excision, laser coagulation, laser vaporization, or photodynamic therapy (PDT). For these purposes, the carbon dioxide laser, the neodymium:yttrium aluminum garnet laser and the argon laser are particularly suitable. PDT is a therapeutic approach based on the photosensitization of the target tissue by topical or systemic photosensitizers and subsequent irradiation with light from a laser or a lamp inducing cell death via generation of reactive oxygen species. Laser therapy and PDT have shown good results in the curative treatment of actinic keratoses, superficial basal cell carcinoma, Bowen's disease and cheilitis actinica. However, they are not recommended for primary malignant melanoma and invasive squamous cell carcinoma. In some patients, lasers and PDT might also be used effectively for the palliative treatment of cutaneous metastases. In selected patients, lasers and PDT may offer some advantages over routine procedures, e.g. reduction of scarring and better cosmetic results. However, when treating invasive tumors with curative intention, one has to bear in mind the lack of histologic control and the limited depth of tissue penetration of most laser and PDT therapies.

Photodynamic therapy: applications in dermatology

Photodynamic therapy (PDT) offers the potential of an effective new treatment in several areas of medicine. Topical photodynamic therapy is practical and non-invasive and is particularly suited to dermatological indications. A variety of pre-malignant and malignant skin lesions including Bowen's disease, actinic keratoses (AKs) and basal cell carcinoma (BCC) have been treated with success. The role of PDT in inflammatory dermatoses remains to be established. The currently available literature is reviewed.

Photodynamic therapy with violet light and topical 6-aminolaevulinic acid in the treatment of actinic keratosis, Bowen's disease and basal cell carcinoma

BACKGROUND

Most clinical studies using photodynamic therapy (PDT) with topical application of delta-aminolaevulinic acid (delta-ALA) use red light because it allows greater depth of penetration. However, given the porphyrin-like spectrum of delta-ALA-induced photosensitivity, violet light provides a maximal overlap with the excitation spectrum of protoporphyrin IX, meaning that PDT with violet light uses less light energy to induce the phototoxic reaction.

AIM

To study the efficacy of violet light in combination with topical delta-ALA PDT in the treatment of pre-malignant and malignant skin lesions.

METHODS

Eight hours after 20% delta-ALA was applied topically, photoirradiation was performed with an incoherent light source (Philips HPM-10, 400 W) emitting predominantly violet light (400-450 nm). Lesions received 10-20 J/cm2 during an exposure time of 30 min. The 38 subjects treated included three with basal cell naevus syndrome with multiple (> 30) superficial and nodular basal cell carcinomas (BCCs), one subject had multiple lesions of Bowen's disease, involving 50% of the scalp, and the remaining 34 subjects presented a total of 35 superficial BCCs, 10 nodular BCCs, four large solar keratoses and five solitary lesions of Bowen's disease.

RESULTS

Complete remission both clinically and histologically was seen after a single treatment in 82% of the superficial BCCs (100% after a second treatment), 50% of the nodular BCCs, one of the four solar keratosis lesions (partial remission in the other three) and 90-100% of the solitary lesions of Bowen's disease.

CONCLUSIONS

delta-ALA PDT using violet light appears to be a well tolerated and effective alternative treatment for premalignant and malignant skin lesions, especially when there are multiple lesions or large patches comprising a large area of skin.

In vitro and in vivo expression of protoporphyrin IX induced by lipophilic 5-aminolevulinic acid derivatives

We estimated the expression level of protoporphyrin IX (PpIX) induced by lipophilic 5-aminolevulinic acid (ALA) derivatives and observed its histological distribution by fluorescence microscopy. In vitro PpIX expression in Hepe2 cells was the highest when induced by ALA pentyl ester. This level was 2.8-fold higher than that induced by ALA after 4 h incubation and 2.5-fold higher than that after 24 h incubation. The differences between ALA pentyl ester and ALA were significant at both time points (P<0.01). In HeLa cells, ALA butyl ester showed the highest induction of PpIX, which was 2.6-fold higher than ALA after 4 h incubation and 3.5-fold higher after 24 h incubation. The differences were significant at both time points (P<0.01). In mice with squamous cell carcinoma, the in vivo expression of PpIX in the tumors was highest with ALA methyl ester, which was 1.3-fold higher than ALA. The difference was significant (P<0.01). The expression of PpIX by means of fluorescence microscopy was highest by ALA methyl ester. Under in vitro conditions, PpIX expression was efficiently induced by long chain ALA esters, while better in vivo PpIX induction was obtained with short chain ALA esters. In this study, ALA methyl ester was found to be the best among the ALA derivatives in inducing PpIX expression in vivo, and would be more effective in treatment of skin cancers than ALA.

Topical 5-aminolevulinic acid and photodynamic therapy in dermatology: a minireview

Photodynamic therapy (PDT) is a treatment modality using a photosensitizer, light and oxygen to cause photochemically induced selective cell death. When exposed to light with the proper wavelength, the topically applied photosensitizer or photosensitizer precursor can activate a biomolecule through electron transfer to yield free radicals or produce singlet oxygen from energy transferred from the excited sensitizer to molecular oxygen. The tissue damage is the result of the activation of reactive singlet oxygen or free radical production. Photodynamic therapy with topical application of 5-aminolevulinic acid (ALA) is a new technique and although it remains largely experimental, it has potential application for treatment of malignant skin tumors, various precancerous and selected benign skin diseases. This technique yields not only a high percentage of good therapeutic results but also excellent cosmetic outcome. This paper reviews the recently published data on clinical ALA-based PDT in dermatology.

A follow-up study of recurrence and cosmesis in completely responding superficial and nodular basal cell carcinomas treated with methyl 5-aminolaevulinate-based photodynamic therapy alone and with prior curettage

BACKGROUND

Methyl 5-aminolaevulinate (mALA) is an ester derivative of 5-aminolaevulinic acid (ALA) with increased lipophilicity compared with ALA.

OBJECTIVES

To assess long-term cure rate, cosmesis, recurrence rate and extent of fibrosis after mALA-based photodynamic therapy (PDT) of superficial and nodular basal cell carcinomas (BCCs) showing early complete response to treatment.

METHODS

Of 350 BCCs treated, 310 responded completely. These were in 59 patients who were followed for 2-4 years (mean 35 months) after mALA-PDT. Nodular tumours were curetted before PDT, and mALA 160 mg g(-1) was applied to all tumours for 24 h or 3 h before illumination from a broad-band halogen light source with light doses from 50 to 200 J cm(-2). Fibrosis was assessed histologically in 23 biopsies.

RESULTS

The overall cure rate for 350 BCCs, including non-responders and recurrences was 79%. Of 310 lesions, 277 (89%) remained in complete response, and the cosmetic outcome was excellent or good in 272 of the completely responding lesions (98%). Histological examination showed dermal fibrosis in one of 23 biopsies.

CONCLUSIONS

We conclude that mALA-based PDT with prior curettage of nodular lesions is a promising new method for the treatment of BCC.

Photodynamic therapy with topical delta-aminolaevulinic acid for the treatment of plantar warts

Treatments currently employed for plantar warts are often painful (electrosurgery, cryotherapy) and not always effective (keratolytic agents). In this paper we investigate the effect of photodynamic therapy (PDT) with topical delta-aminolaevulinic acid (ALA) on plantar warts. In order to remove the superficial hyperkeratotic layer of the warts an ointment containing 10% urea and 10% salicylic acid was applied for 7 days. After gentle curettage, a cream containing 20% ALA was applied under an occlusive dressing for 5 h on 64 warts, while 57 warts (controls) received only the vehicle. Both the ALA-treated warts and the controls were irradiated using a visible light lamp (with a range of 400-700 nm, peaking at 630 nm). The light dose was 50 J/cm(2). Patients were followed-up for 22 months. Two months after the last irradiation session 48 (75.0%) out of 64 ALA-PDT treated warts had resolved. By contrast only 13 (22.8%) of the 57 control warts had done so. During the treatment a few patients complained of a mild burning sensation. The absorption of ALA by the verrucous tissue was demonstrated by in vivo fluorescence spectroscopy. This study shows that topical ALA-PDT can be an alternative treatment for plantar warts. Further studies will be necessary in order to optimize the concentration of ALA and duration of treatment.

In vivo pharmacokinetics of protoporphyrin IX accumulation following intracutaneous injection of 5-aminolevulinic acid

Photodynamic therapy with 5-aminolevulinic acid (ALA) derived protoporphyrin IX (PpIX) as photosensitizer is a promising treatment for basal cell carcinomas. Until now ALA has been administered topically as an oil-in-water cream in most investigations. The disadvantage of this administration route is insufficiënt penetration in deeper, nodular tumours. Therefore we investigated intracutaneous injection of ALA as an alternative administration route. ALA was administered in 6-fold in the normal skin of three 6-week-old female Dutch pigs by intracutaneous injection of an aqueous solution of ALA (pH 5.0) in volumes of 0.1-0.5 ml and concentrations of 0.5-2% and by topical administration of a 20% ALA cream. During 8 h fluorescence of ALA derived PpIX was measured under 405 nm excitation. For the injection the measured fluorescence was shown to be dose dependent. All injected doses of 3 mg ALA or more lead to a faster initial increase rate of PpIX synthesis and significantly greater fluorescence than that measured after topical administration of ALA. Irradiation (60 Jcm(-2) for 10 min) of the spots was performed at 3.5 h after ALA administration. After 48 and 96 h visual damage scores were evaluated and biopsies were taken for histopathological examination. After injection of 2 mg ALA or more the PDT damage after illumination was shown to be significantly greater than after topical application of 20% ALA. An injected dose of 10 mg ALA (0.5 ml of a 2% solution) resulted in significantly more tissue damage after illumination than all other injected doses.

Mitochondria-based photodynamic anti-cancer therapy

As photodynamic therapy (PDT) becomes established as a treatment for cancer, there is increasing interest in identifying critical mechanisms of cell killing and understanding the bases for effective photosensitizers. The existence of multiple cellular targets makes it difficult to distinguish the critical events leading to cell death from PDT. However, with more sensitive techniques to detect photosensitizer localization, the isolation of PDT-resistant and -sensitive mutants and the use of innovative molecular and biochemical strategies to map cellular events occurring during and after photosensitization, some order is emerging from the chaos. The subcellular localization of many photosensitizers and the early responses to light activation indicate that mitochondria play a major role in photodynamic cell death. PDT with many agents which damage or inhibit different or multiple mitochondrial targets has many of the desirable characteristics for an effective anti-cancer therapy.

Photodynamic therapy with meta-tetrahydroxyphenylchlorin for basal cell carcinoma: a phase I/II study

BACKGROUND

Photodynamic therapy (PDT) is a convenient and effective method of treating small superficial tumours. New second-generation photosensitizers offer some advantages over first-generation sensitizers such as haematoporphyrin derivatives.

OBJECTIVES

To define the optimal treatment parameters (drug dose, light dose and time interval) using meta-tetrahydroxyphenylchlorin (mTHPC) as a photosensitizer in patients with multiple basal cell carcinomas (BCCs).

METHODS

Light of 652 nm (100 mW cm(-2)) was used for illuminating different tumours (n = 187) with light doses of 5--15 J cm(-2). Following an intravenous injection of 0.1 mg kg(-1) mTHPC each patient (n = 5) was illuminated on 4 consecutive days. Each day at least three BCCs per patient were treated with PDT.

RESULTS

Response evaluation at 6, 12 and 18 months showed maximum responses for illumination with 10 or 15 J cm(-2) on days 1 or 2 after injection (86% complete responses). Normal tissue reactions (oedema and erythema) around the treatment site were more severe on day 1 than after longer intervals.

CONCLUSIONS

mTHPC is a very effective photosensitizer; short illumination times can result in long-term cures with good cosmetic healing and with skin phototoxicity of short duration.

Photodynamic therapy of actinic keratoses with topical aminolevulinic acid hydrochloride and fluorescent blue light

BACKGROUND

Aminolevulinic acid hydrochloride (ALA, Levulan) applied topically to actinic keratoses (AKs) leads to accumulation of the photosensitizer protoporphyrin IX, which, when activated by exposure to light, eradicates AKs.

OBJECTIVE

We examined the safety and efficacy of photodynamic therapy using topical 20% ALA in a solution formulation and varying blue light doses to treat multiple AKs on the face and scalp.

METHOD

This is a multicenter, investigator-blinded, randomized, vehicle-controlled study.

RESULTS

Thirty-six patients with clinically typical AKs were treated with 20% ALA; 14 to 18 hours later, they were irradiated with a nonlaser fluorescent blue light source. With the optimal light dose of 10 J/cm(2), 88% of the AKs completely cleared 8 weeks after a single photodynamic treatment, compared with 6% after treatment with vehicle and light.

CONCLUSION

Topical ALA PDT using a nonlaser, blue light source is an effective treatment for multiple AKs.

The photosensitizing effect of the photoproduct of protoporphyrin IX

The photodynamic effect of a photoproduct of protoporphyrin IX (PpIX) induced by 5-aminolevulinic acid (ALA) was investigated in WiDr cells, a human adenocarcinoma cell line. The fluorescence excitation and emission spectra of PpIX and the photoproduct were measured. After 1, 3 or 5 min exposure of the ALA-incubated cells to 140 mW/cm(2) light at 635 nm, the photoproduct--the chlorin photoprotoporphyrin (Ppp), had an emission band around 670 nm. The Ppp excitation peak at 670 nm is well separated from the PpIX peak at 635 nm. The outcome of photodynamic therapy (PDT) was determined by measuring intracellular fluorescence intensity of propidium iodide (PI) 2 h following PDT and methylene blue (MB) staining 24 h following PDT. A significant increase in the fluorescence intensity of PI was noted when the ALA-loaded cells were exposed to 670 nm light after exposure to 635 nm, indicating enhanced cell membrane inactivation induced by the photodynamic action of the photoproduct. However, the fraction of the cells that survived following the same treatment as measured by MB staining was not significantly affected based on an analysis of variance. The fluorescence of PpIX decayed significantly during 635 nm light exposure. Exposure to light at 670 nm does not lead to any photodegradation of PpIX. The fluorescence of Ppp was bleached during 670 nm light exposure. Exposure of Ppp at 670 nm gives no PpIX back. Thus, the phototransformation of PpIX to Ppp is probably not a reversible process.

Systemic photodynamic therapy with aminolaevulinic acid delays the appearance of ultraviolet-induced skin tumours in mice

BACKGROUND

Photodynamic therapy (PDT) with topical aminolaevulinic acid (ALA) has recently been approved by the US Food and Drug Administration for the treatment of actinic keratoses.

OBJECTIVES

To determine whether weekly systemic suberythemogenic ALA-PDT could prevent the appearance of ultraviolet (UV) -induced skin tumours in hairless mice.

METHODS

One group of 20 mice received daily UV radiation from FS 20 tubes, and weekly intraperitoneal injections of ALA 40 mg kg(-1), each followed 3 h later by 12 J cm(-2) of white light (ALA-PDT). Control groups consisted of mice exposed only to UV, to UV and ALA without white light, or UV and white light without ALA, as well as untreated mice.

RESULTS

The tumour-free survival was significantly longer for mice exposed to daily UV and weekly ALA-PDT as compared with the control groups. Neither the mortality nor the incidence of large skin tumours was higher in the UV/ALA-PDT group than in mice exposed only to UV. In vivo fluorescence spectroscopy showed that the 635-nm fluorescence emission within tumours was lower than in normal skin 3 h after ALA administration. This was also confirmed by quantitative fluorescence microscopy.

CONCLUSIONS

Systemic ALA-PDT can delay the appearance of UV-induced skin tumours in mice without increasing mortality or the incidence of large tumours.

Topical photodynamic therapy at low fluence rates--theory and practice

Photodynamic Therapy (PDT), with topically applied 5-aminolaevulinic acid as the photosensitiser, is an effective treatment for various malignant and pre-malignant skin conditions. Several studies have shown the importance of fluence rate as well as fluence in the efficacy of PDT. We propose a measure of PDT efficacy, Photodynamic Damage Dose (PDD), which uses the product of instantaneous fluence rates, photosensitiser concentrations and oxygen concentrations in its calculation. We derive a qualitative numerical model of PDT and verify it by demonstrating an inverse fluence rate effect, increased efficacy of fractionated PDT, PDT induced hypoxia, and the dependence of photobleaching on fluence rate under certain circumstances. We recommend that fluence, fluence rate and any fractionation regime used should be detailed when reporting a trial as altering any of these has significant effects on PDT efficacy. The model predicts that low fluence rate irradiations should be as effective as high fluence rate irradiations if carried out over the same length of time. To test this we build a light emitting diode-based lamp (fluence rate of 7 mW cm(-2) at 635 nm) and used it to treat 32 superficial basal cell carcinomas on 22 patients (30 min treatment time, fluence 12.6 J cm(-2)). The complete response rate at one year was 84%, which is comparable to that achieved using higher fluence rate sources for similar treatment times. We conclude that this robust, inexpensive light source is effective for topical PDT.

Photodynamic therapy vs. cryosurgery of basal cell carcinomas: results of a phase III clinical trial

BACKGROUND

A previously reported randomized clinical trial showed treatment of Bowen's disease using photodynamic therapy (PDT) with topically applied delta-aminolaevulinic acid (ALA) to be at least as effective as cryosurgery and to be associated with fewer adverse effects.

OBJECTIVES

To compare ALA-PDT and cryotherapy in the treatment of histopathologically verified basal cell carcinomas (BCCs) in a non-blinded, prospective phase III clinical trial.

METHODS

One lesion from each of 88 patients was included. The BCCs were divided into superficial and nodular lesions. The follow-up period was restricted to 1 year with close follow-up for the first 3 months. Efficacy was assessed as the recurrence rate 12 months after the first treatment session, verified by histopathology. Tolerability was evaluated as the time of healing, pain and discomfort during and after the treatment, and final cosmetic outcome.

RESULTS

Histopathologically verified recurrence rates in the two groups were statistically comparable and were 25% (11 of 44) for ALA-PDT and 15% (six of 39) for cryosurgery. However, clinical recurrence rates were only 5% (two of 44) for PDT and 13% (five of 39) for cryosurgery. Additional treatments, usually one, had to be performed in 30% of the lesions in the PDT group. The healing time was considerably shorter and the cosmetic outcome significantly better with PDT. Pain and discomfort during the treatment session and in the following week were low, and were equivalent with the two treatment modalities.

CONCLUSIONS

In terms of efficacy, ALA-PDT is comparable with cryosurgery as a treatment modality for BCCs. Retreatments are more often required with PDT than with cryosurgery. This can easily be performed due to the shorter healing time, less scarring and better cosmetic outcome that follows ALA-PDT.

Photodynamic therapy of feline superficial squamous cell carcinoma using topical 5-aminolaevulinic acid

A study was undertaken to investigate the treatment of superficial squamous cell carcinoma of the nasal planum, pinna and eyelid in cats by photodynamic therapy, using topical 5-aminolaevulinic acid cream, with subsequent exposure to red light of wavelength 635 nm, supplied by a light-emitting diode source. A total of 13 squamous cell carcinomas were treated, including 10 nasal planum lesions, two pinnal lesions and one eyelid lesion. After a single treatment, complete responses were seen in nine out of 10 nasal planum lesions, one out of two pinnal lesions and the eyelid lesion. The overall complete response rate for lesions managed with a single photodynamic therapy treatment was 85 per cent. Seven of the 11 lesions (63.6 per cent) showing a complete response subsequently recurred; the time to recurrence ranged from 19 to 56 weeks (median 21 weeks, mean 26.7 weeks).

Iontophoretic delivery of 5-aminolevulinic acid (ALA): effect of pH

PURPOSE

To examine the iontophoretic delivery of ALA as a function of pH and to determine the principal mechanisms responsible for its electrotransport.

METHODS

Anodal iontophoretic transport of ALA was measured as a function of its concentration and pH of the donor solution. Experiments were performed in vitro using skin excised from porcine ears as the membrane. To deduce mechanism, the concomitant transport of the electroosmotic marker, mannitol, was also assessed.

RESULTS

ALA iontophoresis at pH 7.4 is a linear function of concentration over the range 1-100 mM. The mechanism was deduced to be electroosmosis. By reducing the pH from 7.4 to 4.0, the dominant mechanism of ALA transport was shifted from electroosmosis to electrorepulsion as the skin's net negative charge was progressively neutralized. However, the total delivery of the compound was not altered by lowering the pH suggesting that the increased electrorepulsive contribution was essentially balanced by the concomitantly reduced electroosmosis.

CONCLUSIONS

Significant ALA delivery at pH 7.4 can be achieved by increasing the drug concentration in the anodal formulation to 100 mM. Lowering the pH does not result in increased ALA transport. Alternative strategies are therefore required to maximize and optimize ALA delivery by iontophoresis.

Bowen's disease, solar keratoses and superficial basal cell carcinomas treated by photodynamic therapy using a large-field incoherent light source

BACKGROUND

Photodynamic therapy (PDT) has not yet been demonstrated to be superior to conventional treatment in the treatment of superficial skin cancers and premalignant skin conditions. A limitation for PDT is the absence to date of a light source suitable for the treatment of larger lesions or 'field changes' where several lesions are present on one anatomical site.

OBJECTIVES

To investigate the safety and efficacy of a large field light source, the Waldmann PDT 1200, in the treatment of Bowen's disease (BD), superficial basal cell carcinomas (BCCs) and solar keratoses (SKs).

METHODS

After application of 5-aminolaevulinic acid for 4-6 h, each lesion was irradiated with 105 J cm-2 of incoherent red light centred on 640 nm. Eighty-eight patients with 239 lesions were recruited.

RESULTS

Within two treatments, 88% of BD lesions, 95% of BCCs and 99% of SKs showed complete clinical clearance. At 12 months the complete response rates were 69% for BD, 82% for BCC and 72% for SK.

CONCLUSIONS

This study confirms that PDT is a useful treatment and that selected superficial BCCs and SKs respond well to PDT. The PDT 1200 light source proved capable of treating multiple lesions amounting to a 'field change' and also lesions up to 10 cm in diameter within an acceptable treatment time. Thus far, PDT has failed to become established as a routine treatment for small premalignant and malignant skin lesions as it has not proved superior to simple cheaper conventional therapies such as cryotherapy, curettage and cautery, topical chemotherapy with 5-fluorouracil, or surgery. However, PDT has become established as a treatment for selected cases in some centres. This study suggests a role for PDT in the treatment of large premalignancies, superficial BCCs and field change where existing treatments may be problematic.

Treatment of multiple scalp basal cell carcinomas by photodynamic therapy

The use of surface protoporphyrin IX fluorescence detection to delineate multiple superficial basal cell carcinomas on a patient's scalp is described. Photodynamic therapy (PDT) was subsequently performed with clearance of six and partial clearance of the remaining two tumours. The treated lesions have not recurred during 12 months of follow-up. The opportunity to combine diagnostic fluorescence detection with subsequent treatment by PDT offers an effective and practical management option. PDT is a tissue-sparing modality with low morbidity and good cosmesis, leading us to propose 5-aminolaevulinic acid-PDT for multiple superficial basal cell carcinomas of the scalp.

Photodynamic therapy of skin cancers: sensitizers, clinical studies and future directives

Photodynamic therapy (PDT) is a new modality of skin cancer treatment. It involves the administration of photosensitizing drugs which, when localized in tumor tissue can produce its destruction by absorbing an adequate dose of light of an appropriate wavelength. A large number of photosensitizing agents have been tested in PDT experiments. Topical application of 5-aminolevulinic acid (5-ALA) followed by light irradiation is the most commonly used method. 5-ALA is a prodrug converted in situ via the heme cycle into protoporphyrin IX, an effective photosensitizer agent. Treatment of nonmelanoma skin cancers by PDT has met with varying degrees of success. In the case of 5-ALA, this therapy's main limitation is the poor penetration of 5-ALA into skin, due to hydrophilic and charge characteristics. However, the efficacy of 5-ALA-PDT may be improved by (a) development of adequate drug delivery systems; (b) use of enhancers of PpIX production and accumulation in target tissue, and (c) modifications of the 5-ALA molecule. Optimal timing, light sources, doses, and number of applications are also important factors for topical 5-ALA therapy and must be well defined. The aim of this review is to highlight recent progress in 5-ALA-PDT of skin cancer, and to present ways holding promise for its improvement.

Routine double treatments of superficial basal cell carcinomas using aminolaevulinic acid-based photodynamic therapy

BACKGROUND

Superficial basal cell carcinomas of the skin (sBCC) often respond poorly to single-treatment aminolaevulinic acid-based photodynamic therapy (ALA-PDT), with a number of reports indicating a relapse rate of 50% or more.

OBJECTIVES

To determine whether a second treatment at seven days can improve the response.

METHODS

Twenty-six lesions were treated twice with ALA-PDT, with an interval of 7 days between the two treatment sessions.

RESULTS

We observed a complete response rate of 100% 1 month after treatment. Only one lesion relapsed (16 months post-PDT), a relapse rate of 4% (median follow up 27 months; range 15-45 months). Cosmetic results were excellent.

CONCLUSIONS

We consider routine double treatments with ALA-PDT to be an effective approach to the management of sBCC, particularly those located in anatomically difficult, or cosmetically sensitive, sites.

Comparison of red and green light in the treatment of Bowen's disease by photodynamic therapy

BACKGROUND

A variety of protocols exist for the treatment of Bowen's disease by photodynamic therapy (PDT) using topical 5-aminolaevulinic acid (5-ALA).

OBJECTIVE

To determine the optimal wavelength (red or green light) for this treatment.

METHODS

A randomized comparison study of ALA-PDT using red (630 +/- 15 nm) or green (540 +/- 15 nm) light in the treatment of Bowen's disease.

RESULTS

The initial clearance rate for lesions treated by red light was 94% (30 of 32) in comparison with 72% (21 of 29) for those lesions receiving green light (P = 0.002). Over the following 12 months, there were two recurrences in the red light group and seven in the green light group reducing the clearance rates to 88% and 48%, respectively. The frequency and severity of pain experienced were similar between the two treatment groups. No hyperthermia, nor significant difference in lesional temperatures, was observed between the wavelengths studied.

CONCLUSION

Green light is less effective than red light, at a theoretically equivalent dose, in the treatment of Bowen's disease by topical ALA-PDT.

Comparison of cryotherapy with curettage in the treatment of Bowen's disease: a prospective study

BACKGROUND

In our departments, curettage and cautery (C&C) and liquid nitrogen cryotherapy are the preferred methods of treatment for Bowen's disease (BD).

OBJECTIVES

We aimed to compare these two treatments with regard to efficacy, time to heal, morbidity and recurrence rate.

METHODS

Cryotherapy was performed using a liquid nitrogen spray giving two freeze-thaw cycles, each freeze cycle being maintained for 5-10 s after the formation of an ice ball to the intended margin. Curettage was performed with a conventional disposable curette under local anaesthesia, and electrocautery was then used for haemostasis.

RESULTS

Eighty lesions in 67 patients (55 female) were analysed. The mean age of the patients was 74 years (range 46-89). The most frequent site was the lower leg, below the knee (n = 59, 74%). The average time taken for complete healing after the procedure was 60 days. The mean size of the lesions was 336 mm(2) (range 30-1890). The patients were followed up for a mean of 22 months (range 6-24, median 2 years). In the cryotherapy group (n = 36 lesions), the median time to complete healing was 46 days (range 14-210; mean 69). Twelve lesions took more than 90 days to heal. Infection requiring antibiotics developed in four patients. Thirteen of the treated lesions had recurred by 24 months. In the C&C group (n = 44 lesions), the median time to healing was 35 days (range 14-330; mean 53). Six of the lesions took more than 90 days to heal. Infection developed in two patients. Recurrence occurred in four lesions over the follow-up period. Considering BD on the lower legs separately, lesions took on average 90 days to heal in the cryotherapy group (n = 23), whereas in the C&C group (n = 36) they took 39 days to heal (P < 0.001). During the procedure and the subsequent 24 h, patients were 10.4 times more likely to report pain of any degree for lesions treated by cryotherapy than by C&C (P < 0.001).

CONCLUSIONS

This study suggests a superiority of C&C over cryotherapy in the treatment of BD, especially for lesions on the lower leg. Curettage of lesions of BD is associated with a significantly shorter healing time, less pain, fewer complications and a lower recurrence rate when compared with cryotherapy.

Photodynamic therapy of cutaneous lymphoma using 5-aminolevulinic acid topical application

BACKGROUND

Photodynamic therapy (PDT) with topical application of 5-aminolevulinic acid (ALA) is a new and effective modality for treatment of superficial basal and squamous cell carcinomas.

OBJECTIVE

We present the kinetics of ALA-induced protoporphyrin IX (PP) accumulation and the results of ALA PDT treatment on two patients with different stages (stage I and stage III) of mycosis fungoides (MF)-type cutaneous T-cell lymphoma (CTCL).

METHODS

ALA-Decoderm cream was applied to the lesions for 16 hours. Spectrofluorescence measurements of PP accumulation were carried out before, during, and 1 hour after photoirradiation (580-720 nm) using the VersaLight system.

RESULTS

Different patterns of PP fluorescence kinetics were observed in patients with early and advanced stages of the disease. During photoirradiation the intensity of fluorescence decreased depending on the lesion thickness. One hour after the photoirradiation procedure no PP fluorescence was observed in the stage I MF lesion, while in the thick stage III MF lesions, PP fluorescence reappeared; after an additional 10-15 minutes of irradiation PP fluorescence disappeared. Complete response with excellent cosmetic results was observed in the stage I lesion after a single irradiation with a light dose of 170 J/cm2; in five stage III lesions, complete response was achieved after fractionated irradiation with a total light dose of 380 J/cm2 (follow-up at 27 and 24 months, respectively).

CONCLUSION

The results showed a high response of both stage I and stage III MF lesions to ALA PDT. This modality appears to be very effective and can be used successfully for MF treatment.

Laser-induced fluorescence studies of normal and malignant tumour tissue of rat following intravenous injection of delta-amino levulinic acid

BACKGROUND AND OBJECTIVE

Laser-induced fluorescence was studied in normal and tumour tissue of rat after intravenous injection of delta-amino levulinic acid (ALA). The aim of the study was to investigate the protoporphyrin IX accumulation in different tissue types in rat after systemically administered ALA.

STUDY DESIGN/MATERIAL AND METHODS

A malignant rat tumour and normal tissue from 13 different organs were investigated in eight rats. The rats were injected with two different ALA doses, 30 and 90 mg/kg b.w., and the investigations were performed at 10, 30 and 240 min after the injection. The fluorescence was recorded utilising an optical fibre based fluorosensor at 405 nm excitation.

RESULTS

Fluorescence spectra were recorded in the 400-750 nm wavelength region including the dual-peaked PpIX fluorescence at about 635 and 705 nm, and the tissue autofluorescence peaking at about 500 nm. The maximum tumour build-up of PpIX was achieved already in less than 1 hr after ALA injection. The fluorescence demarcation between tumour and surrounding tissue was a factor of 7-8:1 after 30 min and decreased for longer retention times. The accumulation in 13 different organs was investigated and a particularly high PpIX build-up was found in stomach and intestine.

CONCLUSIONS

Fluorescence detection following i.v. injection of ALA provides attractive diagnostics for the experimental tumour used, indicating clinical usefulness.

Penetration of the laser light into the skin in vitro

BACKGROUND AND OBJECTIVE

Knowledge of the optical parameters of the skin is important for all kinds of phototherapy. We analyzed penetration of laser light and proved different optical properties of in vitro specimens of normal skin and granular tissue from skin ulcers.

STUDY DESIGN/MATERIALS AND METHODS

An He-Ne laser (lambda = 632.8 nm, output 50 mW) and a semiconductor laser (lambda = 675 nm, output 21 mW) were used. The distribution of laser radiation was detected by a CCD camera and evaluated by the image analysis software DIPS.

RESULTS

Transmittance in granular tissue was about 2.5 times higher than that in normal skin. In the thickest skin sample (2 cm), approximately 0.3% of He-Ne laser and 2.1% of semiconductor laser light penetrated.

CONCLUSIONS

The results demonstrate the percentage of incident light penetrating the individual skin layers in different localizations on the skin surface, which is a decisive factor for the selection of the radiation dose.

Laser Doppler perfusion imaging: new technique for determination of perfusion and reperfusion of splanchnic organs and tumor tissue

BACKGROUND AND OBJECTIVE

Several investigations indicated that laser Doppler flowmetry on the liver surface reflects relative changes of the total liver blood flow. In this study, Laser Doppler Perfusion Imaging (LDI), monitoring the surface only, was used for measurements of tissue perfusion of normal and/or impaired liver, pancreas, spleen, stomach and intestines, and the blood flow of hepatic tumors in rats.

STUDY DESIGN/MATERIALS AND METHODS

Eighty Wistar/Furth rats were divided into five groups. Group I served as controls. Groups II and III underwent ischemic injury of the liver and intestine with or without the administration of WEB2170, a platelet-activating factor receptor antagonist. Laser-induced photodynamic therapy (PDT) utilizing delta-amino levulinic acid sensitization was performed in Groups IV and V.

RESULTS

Normal pancreas and intestine had a high LDI perfusion value and the liver and stomach exhibited a medium perfusion value whereas the perfusion value from the spleen was low. WEB2170 improved the reperfusion of the postischemic liver and intestine. An immediate decrease in surface blood flow of hepatic tissue treated by laser-induced PDT and a decreased blood flow in large tumors were observed.

CONCLUSION

LDI is a useful technique for the measurement of tissue perfusion of various splanchnic organs or tumor tissues.

Delta-aminolevulinic acid in superficial basal cell carcinomas and normal skin-a microdialysis and perfusion study

Delta-aminolevulinic acid (ALA) is used for photodynamic therapy of basal cell carcinoma (BCC) as it is converted to protoporphyrin IX in tumour tissue. During illumination with 635 nm light a photochemical reaction takes place, singlet oxygen is generated and the tumour destroyed. In this study we used the microdialysis technique to quantify the concentration of ALA at a certain depth in tumour and healthy skin. The penetration ability of ALA was investigated as a function of time in BCCs (n = 14) and in normal skin (n = 4) after topical application. The microdialysis catheters were inserted intracutaneously and the depth position recorded by means of ultrasound. Microdialysate sample concentrations of amino acids and ALA were determined by high performance ion-exchange chromatography. A laser Doppler perfusion imager measured perfusion in the BCCs. The data show that the average depth of the microdialysis catheters was 0.5 mm. The interstitial ALA concentration in the BCCs increased from 0 to 3.1 mmol/L 15 min after application of ALA, whereas no measurable amounts of ALA were found in healthy skin. The blood perfusion was 2.5-fold increased in the BCCs. The interstitial levels of amino acids were not significantly changed during the ALA treatment. In summary, we found that ALA rapidly penetrates tumour skin. We conclude that microdialysis seems to be well suited for pharmacodynamic studies of ALA in skin.

Photodynamic therapy of superficial basal cell carcinoma with 5-aminolevulinic acid with dimethylsulfoxide and ethylendiaminetetraacetic acid: a comparison of two light sources

The aim of this prospective randomized study was to compare the clinical and cosmetic outcome of superficial basal cell carcinomas (BCC), using either laser or broadband halogen light, in photodynamic therapy with topical 5-aminolevulinic acid (ALA). A total of 83 patients with 245 superficial BCC were included in the study. Standard treatment involved 15 min of local pretreatment with 99% dimethylsulfoxide (DMSO) before topical application of 20% ALA with DMSO (2%) and ethylendiaminetetraacetic acid (2%) as cofactors for 3 h before light exposure with either laser or a broadband lamp (BL). A complete response was achieved in 95 lesions (86%) in the laser group and 110 lesions (82%) in the BL group 6 months after treatment. Of these, 80 lesions (84%) in the laser group and 101 lesions (92%) in the lamp group were independently evaluated to have an excellent or good cosmetic post-treatment score. No serious adverse events were reported. This study shows that there is no statistical significant difference in cure the rate (P = 0.49) and the cosmetic outcome (P = 0.075) with topical application of a modified ALA-cream between light exposure from a simple BL with continuous spectrum (570-740 nm) or from a red-light laser (monochromatic 630 nm). Cost and safety are further elements in favor of the BL in this setting.

Combination effect of photodynamic and sonodynamic therapy on experimental skin squamous cell carcinoma in C3H/HeN mice

We studied a combination of photodynamic therapy (PDT) and sonodynamic therapy (SDT) for improving tumoricidal effects in a transplantable mouse squamous cell carcinoma (SCC) model. Two sensitizers were utilized: the pheophorbide-a derivative PH-1126, which is a newly developed photosensitizer, and the gallium porphyrin analogue ATX-70, a commonly used sonosensitizer. Mice were injected with either PH-1126 or ATX-70 i.p. at doses of 5 or 10 mg/kg.bw. At 24 (ATX-70) or 36 hr (PH-1126) (time of optimum drug concentration in the tumor) after injection, SCCs underwent laser light irradiation (88 J/cm2 of 575 nm for ATX-70; 44J/cm2 of 650 nm for PH-1126) (PDT), ultrasound irradiation (0.51 W/cm2 at 1.0 MHz for 10 minutes) (SDT), or a combination of the two treatments. The combination of PDT and SDT using either PH-1126 or ATX-70 as a sensitizer resulted in significantly improved inhibition of tumor growth (92-98%) (additive effect) as compared to either single treatment (27-77%). The combination using PH-1126 resulted in 25% of the treated mice being tumor free at 20 days after treatment. Moreover, the median survival period (from irradiation to death) of PDT + SDT-treated mice (> 120 days) was significantly greater than that in single treatment groups (77-95 days). Histological changes revealed that combination therapy could induce tumor necrosis 2-3 times as deep as in either of the single modalities. The combination of PDT and SDT could be very useful for treatment of non-superficial or nodular tumors.

In vitro fluorescence, toxicity and phototoxicity induced by delta-aminolevulinic acid (ALA) or ALA-esters

Synthesis of delta-aminolevulinic acid (ALA) derivatives is a promising way to improve the therapeutic properties of ALA, particularly cell uptake or homogeneity of protoporphyrin IX (PpIX) synthesis. The fluorescence emission kinetics and phototoxic properties of ALA-n-pentyl ester (E1) and R,S-ALA-2-(hydroxymethyl) tetrahydrofuranyl ester (E2) were compared with those of ALA and assessed on C6 glioma cells. ALA (100 micrograms/mL), E1 and E2 (10 micrograms/mL) induced similar PpIX-fluorescence kinetics (maximum between 5 and 7 h incubation), fluorescence being limited to the cytoplasm. The 50% lethal dose occurred after 6 h with 45, 4 and 8 micrograms/mL of ALA, E1 and E2, respectively. ALA, E1 and E2 induced no dark toxicity when drugs were removed after 5 min of incubation. However, light (25 J/cm2) applied 6 h after 5 min incubation with 168 micrograms/mL of each compound induced 85% survival with ALA, 27% with E1 and 41% with E2. Increasing the incubation time with ALA, E1 and E2 before washing increased the phototoxicity, but E1 and E2 remained more efficient than ALA, regardless of incubation time. ALA-esters were more efficient than ALA in inducing phototoxicity after short incubation times, probably through an increase of the amount of PpIX synthesized by C6 cells.

Photodynamic therapy with 5-aminolaevulinic acid or placebo for recalcitrant foot and hand warts: randomised double-blind trial

BACKGROUND

Photodynamic therapy (PDT) with topical 5-aminolaevulinic acid (ALA) followed by irradiation with incoherent light (ALA-PDT) for recalcitrant warts have had beneficial results. Therefore, we undertook a randomised, parallel, double-blind clinical trial of ALA-PDT versus placeboPDT for recalcitrant foot and hand warts.

METHODS

Recalcitrant foot and hand warts were randomly assigned to six repetitive ALA-PDT or placebo-PDT interventions combined with standard treatment encompassing paring followed by a keratolytic (Verucid). Standardised photographs of each wart were taken before, during (week 7) and after treatment (weeks 14 and 18). The area of each wart compared with entry area was the primary outcome variable, measured from photographs by an evaluator unaware of treatment allocation for intervention. Pain intensity immediately and 24 h after each intervention was assessed by a five-point scale.

FINDINGS

A total of 232 foot and hand warts in 45 patients were entered into the trial: 117 warts were allocated to ALA-PDT and 115 warts to placebo-PDT. In week 14, the median relative reduction in wart area was 98% in the ALA-PDT group (interquartile range 100%, 55%) versus 52% (100%, 0) in the placebo group (p=0.0006). In week 18, the median relative reduction in wart area was 100% in the ALA-PDT group (100%, 57%) versus 71% (100%, 0) in the placebo-PDT arm (p=0.008). Both the number of vanishing warts and the difference in relative wart area of persisting warts at week 14 and 18 were significant (p<0.05) in favour of ALA-PDT. Significantly more ALA-PDT warts were graded at a higher pain intensity after treatment than placebo-PDT warts.

INTERPRETATION

ALA-PDT is superior to placebo-PDT when both wart area and number of vanishing warts are considered.

Photodynamic therapy in dermatology

The combination of light and chemicals to treat skin diseases is widely practiced in dermatology. Within this broad use of light and drugs, in recent years the concept of photodynamic therapy (PDT) has emerged. PDT is a promising modality for the management of various tumors and nonmalignant diseases, based on the combination of a photosensitizer that is selectively localized in the target tissue and illumination of the lesion with visible light, resulting in photodamage and subsequent cell death. Moreover, the fluorescence of photosensitizing compounds is also utilized as a helpful diagnostic tool for the detection of neoplastic tissue. Intensive basic and clinical research culminated in the worldwide approval of PDT for bladder, esophageal, and lung cancer. The expanding use of this relatively new therapeutic modality in dermatology at many centers around the world has revealed its efficacy for the treatment of cutaneous precancer and cancer, as well as selected benign skin disorders. The following article summarizes the main principles of PDT considering the most recent developments and provides a comprehensive synopsis of the present status of the use of PDT in dermatology. (J Am Acad Dermatol 2000;42:389-413.)

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should be able to describe the basic concepts of PDT, including fundamental knowledge of the most relevant photosensitizers, the light sources, the mechanisms involved in PDT-mediated cell destruction, as well as the indications and limitations of photodynamic treatment of skin diseases.

Preliminary evaluation of two fluorescence imaging methods for the detection and the delineation of basal cell carcinomas of the skin

BACKGROUND AND OBJECTIVE

Fluorescence techniques can provide powerful noninvasive means for medical diagnosis, based on the detection of either endogenous or exogenous fluorophores. The fluorescence of delta-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) has already shown promise for the diagnosis of tumors. The aim of the study was to investigate the localization of skin tumors after the topical application of ALA, by detecting the PpIX fluorescence either in the spectral or in the time domain. STUDY DESIGN/MATERIALS N AND METHODS: Two fluorescence imaging systems were used to identify basal cell carcinomas of the skin in humans, after topical application of 20% ALA ointment. Both systems rely on the comparison between the exogenous and the endogenous fluorescence, performed either in the spectral domain or in the time domain. The first system works by using three images acquired through different spectral filters, whereas the second one measures the spatial map of the average fluorescence lifetime of the sample.

RESULTS

A clear demarcation of skin malignancies was successfully performed in vivo noninvasively with both fluorescence imaging systems.

CONCLUSION

The two complementary approaches considered in the present study show promise for skin tumor detection and delineation based on specific fluorescence features.

Photodynamic therapy with delta-aminolaevulinic acid for nodular basal cell carcinomas using a prior debulking technique

The incidence of basal cell carcinomas (BCCs) is still increasing, and there is a demand for an easy, effective and selective non-invasive treatment such as topical photodynamic therapy (PDT). Twenty-three patients with 24 nodular BCCs were treated once with delta-aminolaevulinic acid (delta-ALA) PDT (100 mW cm(-2), 120 J/cm2) 3 weeks after prior debulking of the BCCs. Three months after PDT, all lesions were surgically excised and histopathologically evaluated for residual tumour. Twenty-two (92%) of the 24 nodular BCCs showed a complete response on clinical and histopathological examination. PDT for superficially abraded nodular BCCs with topically applied delta-ALA and the VersaLight as light source is an easy, effective and safe therapy, with excellent cosmetic results and no serious side-effects, in cases where non-surgical treatment of BCCs is indicated.

Emerging new therapies for cutaneous T-cell lymphoma

Improved therapy for CTCL will depend on a better understanding of the pathogenesis of this disease at a molecular level. It is clear that the T cells in MF and CTCL do not undergo normal programmed cell death and have prolonged lifespans. Skin flora or other antigens may stimulate the initial proliferation, offering another approach to change the course of the disease. There has been tremendous interest in biological response modifiers, and the first targeted fusion toxin to activated T cells has been approved for CTCL. New retinoids with increased selectivity and decreased side effects are being tested for this disease. In summary, the treatment of CTCL should continue to improve and should be focused on strategies that preserve the immune function in these patients.

In vitro and in vivo evaluation of hypericin for photodynamic therapy of equine sarcoids

The therapeutic potential of the photodynamic compound, hypericin, in the treatment of equine sarcoids was evaluated. The in vitro cytotoxicity was assessed using three equine cell lines and the observed phototoxic effect was comparable to that on different highly sensitive human cell lines and significantly influenced by the energy density used although independent of the cell type. The in vivo antitumoural action of photodynamic therapy using hypericin was evaluated on three equine sarcoids in a donkey. Four intratumoural injections were given and the tumours were illuminated daily during 25 days. An 81% reduction in tumour volume was obtained at the end of therapy and 2 months later, a 90% reduction was observed. Further experimental work should be performed, but these results suggest that photodynamic therapy using hypericin has a potential for the non-invasive treatment of equine sarcoids.

Repeated 5-aminolevulinic acid-based photodynamic therapy following electro-curettage for pigmented basal cell carcinoma

5-Aminolevulinic acid-based photodynamic therapy (ALA-PDT) in the standard manner is ineffective for pigmented basal cell carcinoma (pBCC), because melanin absorbs the photoactivating light interred for protoporphyrin IX. The objective of this study was to assess the therapeutic outcome of pBCCs with repeated ALA-PDT following removal of pigmentation with electro-curettage. After electro-curettage, 16 pBCCs were treated with a combination of topical application of 20% ALA in O/W emulsion and topical instillation of 10% ALA solution, followed by photoactivating light. ALA-PDT was performed more than three times. Fourteen of 16 pBCCs showed CR. Two pBCCs showing PR or NR were excised. Repeated ALA-PDT following electro-curettage was effective for pBCC.

Guidelines for management of Bowen's disease. British Association of Dermatologists

These guidelines for management of Bowen's disease have been prepared for dermatologists on behalf of the British Association of Dermatologists. They present evidence-based guidance for treatment, with identification of the strength of evidence available at the time of preparation of the guidelines, and a brief overview of epidemiological aspects, diagnosis and investigation.