Distribution of 5-aminolevulinic acid-induced porphyrins in noduloulcerative basal cell carcinoma

Jet-injection assisted photodynamic therapy for superficial and nodular basal cell carcinoma: A pilot study

BACKGROUND

Photodynamic therapy (PDT) with topical δ-Aminolevulinic acid (ALA) has efficacy in treating basal cell carcinoma (BCC) but is limited by incomplete penetration of ALA into the deeper dermis. This prospective open-label pilot trial investigated the safety and efficacy of photosensitizer jet injection for PDT (JI-PDT) for BCC treatment. It was performed with 15 patients (n = 15) with histologically confirmed, untreated, low-risk nodular BCCs at a single institution.

METHODS

For the intervention, JI-PDT patients (n = 11) received two sessions of jet-injected ALA with PDT separated by four to 6 weeks. To further understand treatment technique, another group of patients (n = 4) received jet-injected ALA followed by tumor excision and fluorescence microscopy (JI-E). Treatment tolerability was assessed by local skin responses (LSR) score at five distinct time intervals. Fluorescence microscopy assessed protoporphyrin IX penetration depth and biodistribution within the tumor. At the primary endpoint, tumor clearance was evaluated via visual inspection, dermoscopy and reflectance confocal microscopy. Postinjection and postillumination pain levels, and patient satisfaction, were scored on a 0-10 scale.

RESULTS

Fifteen participants with mean age of 58.3, who were 15/15 White, non-Hispanic enrolled. The median composite LSR score immediately after JI-PDT was 5 (interquartile range [IQR] = 3) which decreased to 0.5 (IQR = 1) at primary endpoint (p < 0.01). Immunofluorescence of excised BCC tumors with jet-injected ALA showed photosensitizer penetration into papillary and reticular dermis. Of the 13 JI-PDT tumors, 11 had tumor clearance confirmed, 1 recurred, and 1 was lost to follow-up. 1/11 patients experienced a serious adverse event of cellulitis. 70% of patients had local scarring at 3 months. Patients reported an average pain level of 5.6 (standard deviation [SD] = 2.3) during jet injection and 3.7 (SD = 1.8) during light illumination.

CONCLUSIONS

Jet injection of ALA for PDT treatment of nodular low-risk BCC is tolerable and feasible and may represent a novel modality to improve PDT.

Application of microneedling in photodynamic therapy: A systematic review

BACKGROUND

The application of photodynamic therapy (PDT) is pivotal in the management of diverse dermatologic conditions. Microneedling (MN) is a minimally invasive tool that is capable of inducing transient pores on the skin to facilitate transdermal drug delivery. Several studies have reported augmentation of PDT combined with MN. This systematic review analyzes the current studies on the efficacy and safety of MN-assisted PDT for skin diseases.

METHODS

The literature search using the PRISMA standard was completed through PubMed, Embase, Web of Science and CENTRAL from the establishment of the databases to November 2023. Two independent researchers finished the procedure.

RESULTS

A total of 12 articles and 413 subjects met our study criteria. This systematic review suggests that MN-assisted PDT can decrease the incubation time required for the photosensitizer and reduce skin lesions of actinic keratosis (AK) . The common side effect is pain and no serious adverse events were reported.

CONCLUSIONS

MN is an effective method to increase the transdermal delivery rate of photosensitizers. For different photosensitizers and disease, MN may show different clinical effects.

Dimethyl sulfoxide (DMSO): a solvent that may solve selected cutaneous clinical challenges

Dimethyl sulfoxide (DMSO) is a clear, odorless liquid, inexpensively produced as a by-product of the wood pulp industry. DMSO's unique chemical properties allow for its broad applications in a wide variety of cutaneous challenges. Widely available in the USA as a solvent, DMSO is FDA-approved only for the treatment of interstitial cystitis and for use as a preservative for organ transplant. DMSO readily penetrates and diffuses through biological membranes. At low concentrations, DMSO exhibits anti-inflammatory, analgesic, diuretic, vasodilator, anti-platelet aggregation, radio-protective, and muscle-relaxing properties. DMSO is also a vigorous scavenger of hydroxyl free radicals, which may explain its observed beneficial effects on skin rejuvenation and recovery from thermal injury. DMSO has a relatively low level of toxicity. DMSO has shown promise in the off-label treatment of basal cell carcinoma, pressure ulcers, scleroderma, herpes simplex, cutaneous fungal infections, and amyloidosis. The potential of DMSO to serve as an independent or adjuvant topical treatment for these conditions is explored in this review.

5-Aminolevulinic Acid as a Theranostic Agent for Tumor Fluorescence Imaging and Photodynamic Therapy

5-Aminolevulinic acid (ALA) is a naturally occurring amino acid synthesized in all nucleated mammalian cells. As a porphyrin precursor, ALA is metabolized in the heme biosynthetic pathway to produce protoporphyrin IX (PpIX), a fluorophore and photosensitizing agent. ALA administered exogenously bypasses the rate-limit step in the pathway, resulting in PpIX accumulation in tumor tissues. Such tumor-selective PpIX disposition following ALA administration has been exploited for tumor fluorescence diagnosis and photodynamic therapy (PDT) with much success. Five ALA-based drugs have now received worldwide approval and are being used for managing very common human (pre)cancerous diseases such as actinic keratosis and basal cell carcinoma or guiding the surgery of bladder cancer and high-grade gliomas, making it the most successful drug discovery and development endeavor in PDT and photodiagnosis. The potential of ALA-induced PpIX as a fluorescent theranostic agent is, however, yet to be fully fulfilled. In this review, we would like to describe the heme biosynthesis pathway in which PpIX is produced from ALA and its derivatives, summarize current clinical applications of ALA-based drugs, and discuss strategies for enhancing ALA-induced PpIX fluorescence and PDT response. Our goal is two-fold: to highlight the successes of ALA-based drugs in clinical practice, and to stimulate the multidisciplinary collaboration that has brought the current success and will continue to usher in more landmark advances.

Biochemical Basis of Selective Accumulation and Targeted Delivery of Photosensitizers to Tumor Tissues

The method of photodynamic therapy for treatment of malignant neoplasms is based on the selective of accumulation of photosensitizers in the tumor tissue. Insufficient selectivity of photosensitizers in relation to pathologically altered tissues and generalized distribution throughout the body leads to the development of severe toxic effects, including skin phototoxicity. The mechanisms underlying selectivity of photosensitizers for tumor tissue include selective binding to blood proteins and lipoproteins (considering that the number of receptors for those is increased on tumor cell membranes), uptake by macrophages, better solubility at low pH (acidic pH is characteristic of tumor cells), and other mechanisms. At present, increase in the efficiency of photodynamic therapy is largely associated with the additional targeting of photosensitizers to tumor tissues. Targeted delivery strategies are based on the differences in metabolism and gene expression profiles between the tumor and healthy cells. There are differences in expression of receptors, proteases, or transmembrane transporters in these cells. In particular, accelerated metabolism in many types of tumors leads to overexpression of receptors for epidermal growth factor, folic acid, transferrin, and a number of other compounds. This review considers biochemical basis for the selective accumulation of various classes of photosensitizers in tumors (chlorins, phthalocyanines, 5-aminolevulinic acid derivatives, etc.) and discusses various strategies of targeted delivery with emphasis on conjugation of photosensitizers with the receptor ligands overexpressed in tumor cells.

Characterization of plasma-derived protoporphyrin-IX-positive extracellular vesicles following 5-ALA use in patients with malignant glioma

BACKGROUND

Malignant gliomas are rapidly progressive brain tumors with high mortality. Fluorescence guided surgery (FGS) with 5-aminolevulinic acid (5-ALA) provides fluorescent delineation of malignant tissue, which helps achieve maximum safe resection. 5-ALA-based fluorescence is due to preferential accumulation of the fluorophore protoporphyrin-IX (PpIX) in malignant glioma tissue. Additionally, gliomas cells release extracellular vesicles (EVs) which carry biomarkers of disease. Herein, we performed animal and human studies to investigate whether 5-ALA dosed glioma cells, in vitro and in vivo, release PpIX positive EVs in circulation which can be captured and analyzed.

METHODS

We used imaging flow cytometry (IFC) to characterize PpIX-positive EVs released from 5-ALA-dosed glioma cells, glioma-bearing xenograft models, as well as patients with malignant glioma undergoing FGS.

FINDINGS

We first show that glioma cells dosed with 5-ALA release 247-fold higher PpIX positive EVs compared to mock dosed glioma cells. Second, we demonstrate that the plasma of glioma-bearing mice (n = 2) dosed with 5-ALA contain significantly higher levels of circulating PpIX-positive EVs than their pre-dosing background (p = 0.004). Lastly, we also show that the plasma of patients with avidly fluorescent tumors (n = 4) undergoing FGS contain circulating PpIX-positive EVs at levels significantly higher than their pre-dosing background (p = 0.00009) and this rise in signal correlates with enhancing tumor volumes (r 2  = 0.888).

INTERPRETATION

Our findings highlight the potential of plasma-derived PpIX-positive EV-based diagnostics for malignant gliomas, offering a novel liquid biopsy platform for confirming and monitoring tumor status.

Ferrochelatase Deficiency Abrogated the Enhancement of Aminolevulinic Acid-mediated Protoporphyrin IX by Iron Chelator Deferoxamine

Aminolevulinic acid (ALA) is a prodrug that is metabolized in the heme biosynthesis pathway to produce protoporphyrin IX (PpIX) for tumor fluorescence detection and photodynamic therapy (PDT). The iron chelator deferoxamine (DFO) has been widely used to enhance PpIX accumulation by inhibiting the iron-dependent bioconversion of PpIX to heme, a reaction catalyzed by ferrochelatase (FECH). Tumor response to DFO treatment is known to be highly variable, and some tumors even show no response. Given the fact that tumors often exhibit reduced FECH expression/enzymatic activity, we examined how reducing FECH level affected the DFO enhancement effect. Our results showed that reducing FECH level by silencing FECH in SkBr3 breast cancer cells completely abrogated the enhancement effect of DFO. Although DFO enhanced ALA-PpIX fluorescence and PDT response in SkBr3 vector control cells, it caused a similar increase in MCF10A breast epithelial cells, resulting in no net gain in the selectivity toward tumor cells. We also found that DFO treatment induced less increase in ALA-PpIX fluorescence in tumor cells with lower FECH activity (MDA-MB-231, Hs 578T) than in tumor cells with higher FECH activity (MDA-MB-453). Our study demonstrates that FECH activity is an important determinant of tumor response to DFO treatment.

Beyond the margins: real-time detection of cancer using targeted fluorophores

Over the past two decades, synergistic innovations in imaging technology have resulted in a revolution in which a range of biomedical applications are now benefiting from fluorescence imaging. Specifically, advances in fluorophore chemistry and imaging hardware, and the identification of targetable biomarkers have now positioned intraoperative fluorescence as a highly specific real-time detection modality for surgeons in oncology. In particular, the deeper tissue penetration and limited autofluorescence of near-infrared (NIR) fluorescence imaging improves the translational potential of this modality over visible-light fluorescence imaging. Rapid developments in fluorophores with improved characteristics, detection instrumentation, and targeting strategies led to the clinical testing in the early 2010s of the first targeted NIR fluorophores for intraoperative cancer detection. The foundations for the advances that underline this technology continue to be nurtured by the multidisciplinary collaboration of chemists, biologists, engineers, and clinicians. In this Review, we highlight the latest developments in NIR fluorophores, cancer-targeting strategies, and detection instrumentation for intraoperative cancer detection, and consider the unique challenges associated with their effective application in clinical settings.

Combination of Sonodynamic and Photodynamic Therapy against Cancer Would Be Effective through Using a Regulated Size of Nanoparticles

Nanoparticles have been used for many functional materials in nano-sciences and photo-catalyzing surface chemistry. The titanium oxide nanoparticles will be useful for the treatment of tumor by laser and/or ultrasound as the sensitizers in nano-medicine. We have studied the combination therapy of photo- and sono-dynamic therapies in an animal tumor model. Oral-administration of two sensitizers titanium oxide, 0.2%-TiO2 nanoparticles for sono-dynamic and 1 mM 5-aminolevulinic acid for photodynamic therapies have resulted in the best combination therapeutic effects for the cancer treatment. Our light microscopic and Raman spectroscopic studies revealed that the titanium nanoparticles were distributed inside the blood vessel of the cancer tissue (1-3 μm sizes). Among these nanoparticles with a broad size distribution, only particular-sized particles could penetrate through the blood vessel of the cancer tissue, while other particles may only exhibit the side effects in the model mouse. Therefore, it may be necessary to separate the optimum size particles. For this purpose we have separated TiO2 nanoparticles by countercurrent chromatography with a flat coiled column (1.6 mm ID) immersed in an ultrasonic bath (42 KHz). Separation was performed with a two-phase solvent system composed of 1-butanol-acetic acid-water at a volume ratio of 4:1:5 at a flow rate of 0.1 ml/min. Countercurrent chromatographic separation yielded fractions containing particle aggregates at 31 and 4400 nm in diameter.

Synthesis of chemically diverse esters of 5-aminolevulinic acid for photodynamic therapy via the multicomponent Passerini reaction

A chemically diverse set of 5-aminolevulinic acid prodrugs were obtained via a Passerini reaction and studied as photodinamic agents in vitro.

Pretreatment with ablative fractional laser changes kinetics and biodistribution of topical 5-aminolevulinic acid (ALA) and methyl aminolevulinate (MAL)

BACKGROUND AND OBJECTIVES

5-Aminolevulinic acid (ALA) and methyl aminolevulinate (MAL) are porphyrin precursors used topically for photodynamic therapy (PDT). Previous studies have established that ablative fractional laser (AFXL) increases topical drug uptake. We evaluated kinetics and biodistribution of ALA- and MAL-induced porphyrins on intact and disrupted skin due to AFXL.

MATERIALS AND METHODS

Two Yorkshire swine were exposed to CO2 AFXL (10.6 µm, 1,850 µm ablation depth) and subsequent topical application of ALA and MAL cream formulations (20%, weight/weight). Porphyrin fluorescence was quantified by digital fluorescence photography (30, 90, and 180 minutes) and fluorescence microscopy at specific skin depths (180 minutes).

RESULTS

Porphyrins gradually formed over time, differently on intact and AFXL-disrupted skin. On intact skin (no AFXL), fluorescence photography showed that MAL initially induced higher fluorescence than ALA (t = 30 minutes MAL 21.1 vs. ALA 7.7 au, t = 90 minutes MAL 39.0 vs. ALA 26.6 (P < 0.009)) but reached similar intensities for long-term applications (t = 180 minutes MAL 56.6 vs. ALA 52 au, P = ns). AFXL considerably enhanced porphyrin fluorescence from both photosensitizers (P < 0.05). On AFXL-exposed skin, MAL expressed higher fluorescence than ALA for short-term application (t = 30 minutes, AFXL-MAL 26.4 vs. AFXL-ALA 14.1 au, P < 0.001), whereas ALA over time overcame MAL and induced the highest fluorescence intensities obtained (t = 180 minutes, AFXL-MAL 98.6 vs. AFXL-ALA 112.0 au, P < 0.001). In deep skin layers, fluorescence microscopy showed higher fluorescence in hair follicle epithelium for ALA than MAL (t = 180 minutes, 1.8 mm, AFXL-MAL 35.3 vs. AFXL-ALA 46.7 au, P < 0.05).

CONCLUSIONS

AFXL changes kinetics and biodistribution of ALA and MAL. It appears that AFXL-ALA favors targeting deep structures.

Poly(L-histidine)-tagged 5-aminolevulinic acid prodrugs: new photosensitizing precursors of protoporphyrin IX for photodynamic colon cancer therapy

Background

5-Aminolevulinic acid (ALA) and its derivatives have been widely used in photodynamic therapy. The main drawback associated with ALA-based photodynamic therapy (ALA-PDT) and ALA fluorescence diagnosis results from the hydrophilic nature of ALA and lack of selectivity for tumor versus nontumor cells. The application of certain triggers, such as pH, into conventional sensitizers for controllable ¹O₂ release is a promising strategy for tumor-targeted treatment.

Methods

A series of pH-sensitive ALA-poly(L-histidine) [p(L-His)_n] prodrugs were synthesized via ring opening polymerization of 1-benzyl-N-carboxy-L-histidine anhydride initiated by the amine hydrochloride group of ALA itself. As an alternative to ALA for PDT, the synthesized prodrugs were used to treat a cultured human colon cancer HCT116 cell line under different pH conditions. The effect of ALA-p(L-His)_n derivatives was evaluated by monitoring the fluorescence intensity of protoporphyrin IX, and measuring the cell survival rate after suitable light irradiation.

Results

The cytotoxicity and dark toxicity of ALA and synthesized ALA-p(L-His) derivatives in HEK293T and HCT116 cells in the absence of light at pH 7.4 and 6.8 shows that the cell viability was relatively higher than 100%. ALA-p(L-His)_n showed high phototoxicity and selectivity in different pH conditions compared with ALA alone. Because the length of the histidine chain increases in the ALA-p(L-His)_n prodrugs, the PDT effect was found to be more powerful. In particular, high phototoxicity was observed when the cells were treated with ALA-p(L-His)¹⁵, compared with treatment using ALA alone.

Conclusion

The newly synthesized ALA-p(L-His)_n derivatives are an effective alternative to ALA for enhancing protoporphyrin IX production and the selectivity of the phototoxic effect in tumor cells.

Treatment with 5-aminolaevulinic acid methylester is less painful than treatment with 5-aminolaevulinic acid nanoemulsion in topical photodynamic therapy for actinic keratosis

BACKGROUND

Topical photodynamic therapy (PDT) is an excellent treatment option for actinic keratosis (AK). Pain is one of the major adverse effects.

OBJECTIVE

To compare the pain intensity during the extensive treatment of cosmetic units using 5-aminolaevulinic acid methylester (MAL) or 5-aminolaevulinic acid nanoemulsion (BF-200-ALA).

METHODS

173 patients with 965 treated areas were enrolled in this retrospective monocentric study. All patients had multiple AKs and received an extensive treatment of the photodamaged area. 424 areas were treated with MAL and 541 with BF-200-ALA. Pain was rated using a standardized visual analogue scale (VAS). The number of PDT treatment interruptions was documented.

RESULTS

PDT with MAL led to a lower mean VAS score (5.0 vs. 5.8), a lower number of treatment interruptions (13.2 vs. 19.9%) and a lower amount of patients experiencing severe pain (25.0 vs. 36.0%) compared to PDT with BF-200-ALA.

CONCLUSION

Our data shows that PDT using MAL is less painful than PDT using BF-200-ALA resulting in a significantly lower mean VAS score (p < 0.001), significantly fewer patients experiencing severe pain (p < 0.001) and a significantly (p < 0.05) lower number of treatment interruptions. Differences in selectivity for tumour cells and transport of ALA in peripheral neurons may play a role.

Monte Carlo modeling of in vivo protoporphyrin IX fluorescence and singlet oxygen production during photodynamic therapy for patients presenting with superficial basal cell carcinomas

We present protoporphyrin IX (PpIX) fluorescence measurements acquired from patients presenting with superficial basal cell carcinoma during photodynamic therapy (PDT) treatment, facilitating in vivo photobleaching to be monitored. Monte Carlo (MC) simulations, taking into account photobleaching, are performed on a three-dimensional cube grid, which represents the treatment geometry. Consequently, it is possible to determine the spatial and temporal changes to the origin of collected fluorescence and generated singlet oxygen. From our clinical results, an in vivo photobleaching dose constant, β of 5-aminolaevulinic acid-induced PpIX fluorescence is found to be 14 ± 1 J/cm(2). Results from our MC simulations suggest that an increase from our typical administered treatment light dose of 75-150 J/cm(2) could increase the effective PDT treatment initially achieved at a depth of 2.7-3.3 mm in the tumor, respectively. Moreover, this increase reduces the surface PpIX fluorescence from 0.00012 to 0.000003 of the maximum value recorded before treatment. The recommendation of administrating a larger light dose, which advocates an increase in the treatment time after surface PpIX fluorescence has diminished, remains valid for different sets of optical properties and therefore should have a beneficial outcome on the total treatment effect.

Development of microemulsions to topically deliver 5-aminolevulinic acid in photodynamic therapy

The aim of this study was to obtain and to characterize microemulsions containing 5-aminolevulinic acid (5-ALA) and to investigate the influence of these systems in drug skin permeation for further topical photodynamic therapy (PDT). 5-ALA was incorporated in water-in-oil (W/O), bicontinuous (Bc), and oil-in-water (O/W) microemulsions obtained by the titration of ethyl oleate and PEG-8 caprylic/capric glycerides:polyglyceryl-6 dioleate (3:1) mixtures with water. Selected systems were characterized by conductivity, viscosity, size of the droplets, and drug release. The stability of the drug in the microemulsions was also assessed. Moreover, the in vitro and in vivo skin permeation of 5-ALA was investigated using diffusion cells and confocal scanning laser microscopy (CSLM), respectively. Despite the fact that the O/W microemulsion decreased the 5-ALA diffusion coefficient and retarded the drug release, it also significantly increased the in vitro drug skin permeation when compared to other 5-ALA carriers. It was observed by CSLM that the red fluorescence of the skin increased homogeneously in the deeper skin layers when the 5-ALA microemulsion was applied in vivo, probably due to the formation of the photoactive protoporphyrin IX. The microemulsion developed carried 5-ALA to the deeper skin layers, increasing the red fluorescence of the skin and indicating the potentiality of the system for topical 5-ALA-PDT.

Photodynamic therapy with intratumoral administration of Lipid-Based mTHPC in a model of breast cancer recurrence

BACKGROUND AND OBJECTIVES

Generalized skin sensitization is a main drawback of photodynamic therapy with systemic administration of photosensitizers. We have evaluated the potential use of an intratumoral injection of a liposomal formulation of mTHPC (Foslip) in a mouse model of local recurrence of breast cancer.

MATERIALS AND METHODS

Mice were directly injected into the tumor (IT) with 25 microl of a Foslip suspension (0.15 mg/ml) and illumination (652 nm, 20 J/cm(2)) was performed at different time points with pathological assessment after 48 hours. In a parallel mice series plasma samples were obtained at different endpoints after IT Foslip injection for HPLC analysis and the tumors were subjected in toto to macrofluorescence imaging. Fluorescence polarization measurements were conducted in vitro to estimate the rate of sensitizer redistribution from liposomes.

RESULTS

Optimal, albeit partial, cure rates were obtained at 24 hours post-sensitizer and uninistration. Inhomogeneous and weak fluorescence was observed at early time points and became maximal at 24 hours. Plasma levels of mTHPC increased until 15 hours. Fluorescence polarization measurements showed a slow sensitizer transfer from liposomes to model membranes.

DISCUSSION AND CONCLUSION

The weak intratumoral fluorescence at early time points could be explained by concentration quenching within the liposomes as evidenced from fluorescence polarization studies. Progressive mTHPC redistribution from liposomes and its further incorporation into tumor tissue resulted in fluorescence build-up over time with a maximum at 24 hours post-injection. This correlates perfectly with the best therapeutic effect at this time point. The absence of total cure can be attributed to inhomogeneous photosensitizer distribution. mTHPC is reabsorbed into the blood stream but the total administered amount is much reduced as opposed to systemic administration so that repeated PDT sessions might be favorable in terms of side effects and tumor response.

5-aminolevulinic acid-conjugated gold nanoparticles for photodynamic therapy of cancer

BACKGROUND

Effective delivery of photosensitizer to target tumor cells that causes minimal damage to healthy cells is an important requirement in photodynamic therapy of cancer.

AIM

We aimed to use biocompatible gold nanoparticles as a vehicle to deliver 5-aminolevulinic (5-ALA) acid for selective and efficient photodynamic therapy.

RESULTS

Protoporphyrin IX accumulated preferentially in fibrosarcoma tumor cells treated with 5-ALA-conjugated nanoparticles while yielding significantly higher reactive oxygen species compared with that with 5-ALA. The elevation of reactive oxygen species resulted in 50% more cytotoxicity to tumor cells than that of 5-ALA alone. Selective destruction of tumor cells was also achieved using 5-ALA-conjugated nanoparticles in co-culture with dermal fibroblasts.

CONCLUSIONS

5-ALA-conjugated nanoparticles offer a new modality for selective and efficient destruction of tumor cells, with minimal damage to fibroblasts in the 5-ALA-photodynamic therapy.

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.

Photodynamic therapy with 5-aminolaevulinic acid, dimethylsulfoxide and curettage in basal cell carcinoma: a 6-year clinical and histological follow-up

BACKGROUND

Long-term follow-up data are needed to evaluate treatment effect after photodynamic therapy (PDT).

OBJECTIVE

To investigate long-term clinical, histological and cosmetic follow-up results in basal cell carcinoma (BCC) after PDT, including treatment response related to patients and lesion characteristics.

MATERIALS AND METHODS

A longitudinal study of 44 patients with 60 histologically verified BCC tumours, treated with one or two sessions of dimethylsulfoxide (DMSO)-supported 5-aminolaevulinic acid--PDT following curettage, was performed. Lesions in complete remission after 3 months were followed with clinical inspection, histological investigation and evaluation of cosmetic outcome at regular intervals; long-term efficacy assessed as verified recurrence within 72 months after PDT.

RESULTS

Complete remission at 3 months was achieved in 55 lesions from 39 patients. Two patients with one lesion each died. At 72 months, 43 of 53 lesions remained disease-free (81%); 68% remained after one treatment session, and 91% remained after two treatment sessions. Recurrence of tumour occurred at 6, 12, 24 and 36 months in 2, 4, 2 and 2 lesions, respectively; clinical investigation identified 97% of them. Male sex and H-mid-face zone were significantly associated with recurrence. The cosmetic outcome at 72 months was rated as good or excellent by patients and investigators in more than 90% of evaluated cases.

CONCLUSION

DMSO-PDT following curettage is an effective treatment for BCC, with favourable long-term clinical, histopathological and cosmetic results. Clinical examination of treated lesions appears to be sufficient for long term follow up.

Bioavailability of aminolaevulinic acid and methylaminolaevulinate in basal cell carcinomas: a perfusion study using microdialysis in vivo

BACKGROUND

Photodynamic therapy is becoming a popular treatment for superficial nonmelanoma precancerous and cancerous lesions, showing excellent cosmetic results. Nevertheless, the reported cure rates vary and the transdermal penetration of drugs has been discussed as a limiting factor, particularly for treatment of nodular basal cell carcinoma (BCC).

OBJECTIVES

To investigate the transdermal penetration of aminolaevulinic acid (ALA) and methylaminolaevulinate (MAL) in BCC in vivo using a microdialysis technique. The different prodrugs were compared and the effect of curettage was studied.

METHODS

Twenty patients with 27 histologically verified BCCs (13 superficial, 14 nodular) were included. All lesions were located at the front of the body (head and face excluded). The first 10 patients included were treated with MAL (13 BCCs), and the following 10 patients with ALA (14 BCCs). A light curettage was performed on every second lesion (curettage, n = 13; noncurettage, n = 14). Microdialysis catheters were inserted into the tumours at tissue depths varying from 0.4 to 1.9 mm. Dialysates were collected at 15-30-min intervals for 4 h and the interstitial concentrations of MAL and ALA were determined using high-performance liquid chromatography.

RESULTS

No significant difference in interstitial drug concentration was observed between lesions treated with ALA or MAL during the 4-h measurement period. However, for the lesions with deeper catheter locations, i.e. at or below 1 mm (n = 11), drug concentrations above the detection limit were obtained in only six lesions. All but one BCC with superficial catheter location, i.e. < 1 mm (n = 16), exhibited detectable drug concentration (P = 0.026). The interstitial peak concentrations were reached within 90 min in 23 of the 27 BCCs, but were not found to be correlated with the depth of the catheters. No difference was found when comparing superficial and nodular BCCs, and the effect of curettage was found to be negligible.

CONCLUSIONS

The results imply that there is no significant difference in transdermal penetration of ALA and MAL in tumour tissue. Detectable levels of drug were not obtained in almost 50% of the lesions where catheters were situated 1-1.9 mm in the lesion. Curettage was not found to affect the interstitial concentration, indicating that penetration of drug indeed might be a problem when treating BCCs thicker than 1 mm.

Comparison of ALA- and ALA hexyl-ester-induced PpIX depth distribution in human skin carcinoma

Photodynamic therapy (PDT) based on the use of photoactivable porphyrins, such as protoporphyrin IX (PpIX), induced by the topical application of amino-levulinic acid (ALA) or its derivatives, ALA methyl-ester (m-ALA), is a treatment for superficial basal cell carcinoma (BCC), with complete response rates of over 80%. However, in the case of deep, nodular-ulcerative lesions, the complete response rates are lower, possibly related to a lower bioavailability of PpIX. Previous in vitro skin permeation studies demonstrated an increased penetration of amino-levulinic acid hexyl-ester (h-ALA) over ALA. In this study, we tested the validity of this approach in vivo on human BCCs. An emulsion containing 20% ALA (w/w) and preparations of h-ALA at different concentrations were applied topically to the normal skin of Caucasian volunteers to compare the PpIX fluorescence intensities with an optical fiber-based spectrofluorometer. In addition, the PpIX depth distribution and fluorescence intensity in 26 BCCs were investigated by fluorescence microscopy following topical application of 20% ALA and 1% h-ALA. We found that, for application times up to 24h, h-ALA is identical to ALA as a PpIX precursor with respect to PpIX fluorescence intensity, depth of penetration, and distribution in basal cell carcinoma, but has the added advantage that much smaller h-ALA concentrations can be used (up to a factor 13). We observed a non-homogenous distribution in BCCs with both precursors, independent of the histological type and depth of invasion in the dermis.

A terapia fotodinâmica com ácido 5-aminolevulínico como modalidade de tratamento para neoplasias cutâneas não-melanoma

FUNDAMENTOS: A terapia fotodinâmica baseia-se na associação de fonte de luz e fotossensibilizador para destruir seletivamente as células. OBJETIVO: Avaliar os efeitos imediatos e tardios, a resposta clínica e os resultados estéticos da terapia fotodinâmica com ácido 5-aminolevulínico em neoplasias cutâneas não-melanoma. MÉTODOS: Trinta e quatro lesões, sendo 19 disceratoses de Bowen e 15 carcinomas basocelulares, foram submetidas à aplicação tópica e oclusiva do ácido 5-aminolevulínico a 20%, por seis horas, e posteriormente a sessão única de laser de diodo (630nm). RESULTADOS: Foram registrados: sensação de queimação durante as sessões; eritema, edema e erosões, nas primeiras 72 horas; cicatrização em média de quatro semanas; resultados estéticos variáveis de excelentes a bons. Aos três meses, a resposta clínica foi de 91,2%, sendo reduzida, aos 18 meses, para 73,3%, de modo similar tanto para disceratose de Bowen (72,2%) quanto para carcinoma basocelular (75%). Foi evidenciada relação de tendência linear entre a redução da freqüência da resposta clínica e o aumento da dimensão das neoplasias cutâneas não-melanoma (p<0,001). CONCLUSÃO: A terapia fotodinâmica com ácido 5-aminolevulínico tópico mostrou destacadas vantagens: minimamente invasiva no tratamento de lesões múltiplas em sessão única ou em sítios de pobre cicatrização com superioridade dos resultados estéticos. O tipo/subtipo(clínico e histopatológico), a dimensão e o adequado seguimento devem ser considerados para a sua indicação no tratamento de neoplasias cutâneas não-melanoma.

Clinical investigation of the novel iron-chelating agent, CP94, to enhance topical photodynamic therapy of nodular basal cell carcinoma

BACKGROUND

Photodynamic therapy (PDT) involves the activation of a photosensitizer by visible light to produce activated oxygen species within target cells, resulting in their destruction. Evidence-based guidelines support the efficacy of PDT using topical 5-aminolaevulinic acid (ALA-PDT) in actinic keratoses, Bowen disease and basal cell carcinoma (BCC). Efficacy for nodular BCC appears inferior to that for superficial BCC unless prior debulking or repeat treatments are performed. Objectives The aim of this study was to assess the safety and efficacy of adding a novel iron-chelating agent, CP94 (1,2-diethyl-3-hydroxypyridin-4-one hydrochloride), to topical ALA, to temporarily increase the accumulation of the photosensitizer in the tumour.

METHODS

A mixed topical formulation of ALA + increasing concentrations of CP94 was used to carry out PDT on previously biopsied nodular BCC with no prior lesion preparation using standard light delivery. The area was assessed clinically and surgically excised 6 weeks later for histological examination.

RESULTS

Enhanced PDT using 40% CP94 resulted in significantly greater clearance rates in nodular BCC than with ALA-PDT alone, in our protocol of single-treatment PDT with no lesion preparation.

CONCLUSIONS

The results of this study demonstrate the safe and effective use of an enhanced ALA-PDT protocol for nodular BCC using CP94, with no adverse reactions to this modification. This is the first time this formulation has been used in patients. This formulation is now the focus of further study.

Derivatives of 5-Aminolevulinic Acid for Photodynamic Therapy

Photodynamic therapy (PDT) is a clinical treatment that combines the effects of visible light irradiation with subsequent biochemical events that arise from the presence of a photosensitising drug (possessing no dark toxicity) to cause destruction of selected cells. Today, the most common agent used in dermatological PDT is 5-aminolevulinic acid (ALA). As a result of its hydrophilic character, ALA penetrates skin lesions poorly when applied topically. Its systemic bioavailability is limited and it is known to cause significant side effects when given orally or intravenously. Numerous chemical derivatives of ALA have been synthesised with the aims of either improving topical penetration or enhancing systemic bioavailability, while reducing side effects. In vitro cell culture experiments with ALA derivatives have yielded promising results. However, if ALA derivatives are to demonstrate meaningful clinical benefits, a rational approach to topical formulation design is required, along with a systematic study aimed at uncovering the true potential of ALA derivatives in photodynamic therapy. With respect to systemic ALA delivery, more study is required in the developing area of ALA-containing dendrons and dendrimers.

Optimized photodynamic therapy with systemic photosensitizer following debulking technique for nonmelanoma skin cancers

BACKGROUND

The thickness and depth of invasion of skin tumors may be limiting factors for topical photosensitizer-based photodynamic therapy (PDT). The use of PDT with systemic photosensitizer needs to be further explored as a modality of treatment for nonmelanoma skin cancer (NMSC).

OBJECTIVE

The objective was to present six patients with multiple, nodular, and/or pigmented NMSC treated successfully with purified hematoporphyrin derivative (PHD) and PDT using prior debulking.

METHODS

After 24 hours of systemic PHD (1.5 mg/kg), 12 lesions of NMSC were selected for PHD-PDT alone and 6 nodular/elevated lesions for PHD-PDT following a debulking procedure. The tumor area was illuminated in one single-dose session of 300 J/cm(2), at an intensity range of 130 to 150 mW/cm(2), with a 630-nm-wavelength diode laser.

RESULTS

The prior curettage provided significant reduction in volume and/or pigmentation of lesions. After the session of PHD-PDT with prior curettage and additional topical 20% ALA-PDT in two lesions or PHD-PDT alone, 83% (5/6) of lesions and 58% (7/12) of lesions, respectively, maintained a complete clinical response, 22.2+/-8.9 months of follow-up.

CONCLUSIONS

The combination of prior debulking with systemic agents-PDT appears to be a good option for multiple, pigmented, and/or nodular lesions of NMSC and can allow the improvement of clinical results.