Photodynamic Therapy

August 05, 2002

MEDLINE Abstracts: Photodynamic Therapy

What's new concerning our understanding of photodynamic therapy? Find out in this easy-to-navigate collection of recent MEDLINE abstracts compiled by the editors at Medscape Dermatology.

Morton CA
J Dermatolog Treat. 2002;13 Suppl 1:25-29

Several open studies report the efficacy of topical photodynamic therapy (PDT) in the treatment of non-melanoma skin cancer and precursor lesions. For a new therapy to change clinical practice, comparison studies with standard therapies are required, assessing efficacy, adverse events and cosmetic outcome. This review considers the evidence for using topical PDT over standard therapies in non-melanoma skin cancer. Limited data indicates topical PDT to be superior to cryotherapy and equivalent to topical 5-fluorouracil in clearing non-hyperkeratotic actinic keratoses, and to achieve a superior cosmetic outcome. Topical PDT is superior to topical 5-fluorouracil, and equivalent to cryotherapy, in the treatment of squamous cell carcinoma in situ (Bowen's disease), again with fewer adverse reactions. Similarly, PDT is as effective as cryotherapy for basal cell carcinoma, but with superior healing and cosmesis. PDT may be particularly advantageous for large and/or multiple lesions and for those in sites where disfigurement or poor healing from conventional therapies is a particular risk. There remains a lack of comparison data concerning routine surgery, curettage, and radiotherapy, but topical PDT would appear as effective as, and in certain aspects superior to, standard therapies in the treatment of non-melanoma skin cancer.

Taylor EL, Brown SB
J Dermatolog Treat. 2002;13 Suppl 1:3-11

Photodynamic therapy (PDT) is being increasingly employed in the detection and treatment of malignant and non-malignant disease. This local technique uses a photosensitizing drug activated by light to generate cell death via the production of reactive oxygen species. This review describes the fundamental processes behind PDT, focussing on the use of 5-aminolevulinic acid (ALA). ALA itself is not a photosensitizing drug, but administration of exogenous ALA induces the build-up of the natural endogenous photosensitizer protoporphyrin IX (PpIX). This form of PDT has proved promising for the treatment of a number of dermatological indications. An overview of these current and potential applications of ALA-based PDT is presented, with emphasis on the advantages of the technique that make it especially suitable for skin conditions and the problem areas on which future research should be focussed.

Leman J, Morton C
Expert Opin Biol Ther. 2002; 2:45-53

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.

Gold MH
Cutis. 2002;69:8-13

The safety and efficacy of treating individuals who presented with multiple actinic keratosis (AK) lesions with 5-aminolevulinic acid (ALA) in combination with photodynamic therapy (PDT) were documented in a phase III trial. This report highlights results of this phase III trial and reviews 2 specific case studies treated with ALA/PDT who presented with both multiple nonhyperkeratotic AK lesions and moderate-to-severe photodamage. Treatment consisted of a 2-step process performed by the investigator. In addition to the pretreatment evaluation, each subject was evaluated at 1- and 2-month intervals after each treatment of ALA/PDT. Clinical findings reveal complete healing at the site of ALA/PDT without scarring or changes in pigmentation, as well as significant changes in signs of photodamage, such as improvement in skin elasticity and reduction in skin thickening.

Fowler JF Jr, Zax RH
Cutis. 2002 ;69:2-7

The safety and efficacy of treating individuals who presented with multiple actinic keratosis (AK) lesions with 5-aminolevulinic acid (ALA) in combination with photodynamic therapy (PDT) were documented in a phase III trial. This report highlights results of this phase III trial and reviews 4 specific cases of sustained AK lesion clearance 4 years after treatment with ALA/PDT Long-term recurrence data were collected from patients who participated in clinical trials of ALA/PDT Long-term evaluation extended to 36 to 48 months (4 years) supports primary efficacy findings of the phase III pivotal trial, with a low incidence of AK recurrence in patients treated with ALA/PDT

: The First Approved Topical Photosensitizer for the Treatment of Actinic Keratosis

Jeffes EW
J Dermatolog Treat. 2002;13 Suppl 1(1):19-23

Actinic keratosis (AK) is a very common skin problem found in patients over 50 years of age, representing an in situ keratinocytic neoplasm that can progress to invasive squamous cell carcinoma of the skin. One Food and Drug Administration-approved treatment for AK of the face and scalp is photodynamic therapy (PDT) with 20% aminolevulinic acid (ALA). This advanced technology has been demonstrated in clinical trials to be effective and well tolerated by patients.

Morton CA, Brown SB, Collins S, et al
Br J Dermato.l 2002;146:552-67

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.

Ibbotson SH
Br J Dermatol. 2002;146:178-188

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.

Lang K, Lehmann P, Bolsen K, Ruzicka T, Fritsch C
Expert Opin Investig Drugs. 2001;10:1139-1156

The role of aminolevulinic acid hydrochloride (ALA) in photodynamic therapy (PDT) of in situ neoplasias and tumours of epithelial tumours is steadily increasing and it has been shown to be the drug with most clinical use in PDT. In dermatology, topical PDT with ALA is already postulated to be the treatment of choice for actinic keratoses and superficial basal cell carcinomas. In gastroenterology, pulmonology, uro- and nephrology, neurology and gynaecology ALA has an important role as a photosensitiser not only in the diagnosis of neoplastic tissue but as therapy; first experiences have been made with PDT in these organs. Besides the therapeutic efficacy of this technique, the fluorescence of ALA-induced porphyrins can be effectively used to detect and delineate epithelial and endothelial neoplasms. In dermatology, other indications for ALA-treatment are non-tumoural applications, especially psoriasis, viral-induced diseases, or acne vulgaris. ALA is an effective compound in the diagnosis or therapy of various epithelial and endothelial neoplastic lesions.


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