Melanoma: Brown SB

Morton CA, Brown SB, Collins S, Ibbotson S, Jenkinson H, Kurwa H, Langmack K, McKenna K, Moseley H, Pearse AD, Stringer M, Taylor DK, Wong G, Rhodes LE. · Department of Dermatology, Falkirk Royal Infirmary, Falkirk FK1 5QE, U.K. · Br J Dermatol. · Pubmed #11966684 No free full text.

Abstract: 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.

Brown SB, Brown EA, Walker I. · Centre for Photobiology and Photodynamic Therapy, School of Biochemistry and Microbiology, University of Leeds, UK. · Lancet Oncol. · Pubmed #15288239 No free full text.

Abstract: It is more than 25 years since photodynamic therapy (PDT) was proposed as a useful tool in oncology, but the approach is only now being used more widely in the clinic. The understanding of the biology of PDT has advanced, and efficient, convenient, and inexpensive systems of light delivery are now available. Results from well-controlled, randomised phase III trials are also becoming available, especially for treatment of non-melanoma skin cancer and Barrett's oesophagus, and improved photosensitising drugs are in development. PDT has several potential advantages over surgery and radiotherapy: it is comparatively non-invasive, it can be targeted accurately, repeated doses can be given without the total-dose limitations associated with radiotherapy, and the healing process results in little or no scarring. PDT can usually be done in an outpatient or day-case setting, is convenient for the patient, and has no side-effects. Two photosensitising drugs, porfirmer sodium and temoporfin, have now been approved for systemic administration, and aminolevulinic acid and methyl aminolevulinate have been approved for topical use. Here, we review current use of PDT in oncology and look at its future potential as more selective photosensitising drugs become available.

Brown SB. · Centre for Photobiology and Photodynamic Therapy, School of Biochemistry and Molecular Biology University of Leeds, UK. · J Dermatolog Treat. · Pubmed #14522636 No free full text.

Abstract: Photodynamic therapy (PDT) is a developing approach to the treatment of cancer and other diseases that involves the use of light to activate photosensitizer molecules. The light energy absorbed by the photosensitizer is transferred to molecular oxygen, which is converted into the highly reactive and cytotoxic species, singlet oxygen. Topical agents such as aminolevulinic acid (ALA) or methyl aminolaevulinate (MAL) may be used for PDT of non-melanoma skin cancers (NMSC) because, in vivo, these agents stimulate the production of porphyrins which act as powerful photosensitisers. This brief review focuses on the use of light to activate MAL, which is now an approved drug (Metvix for certain NMSCs in the European Union. Porphyrins produced by the action of MAL can be activated using red light, which is also capable of deeply penetrating the skin. A number of light sources are available for treatment of NMSC using MAL, including very convenient non-laser sources such as non-coherent filtered lamps and, more recently, sources containing arrays of light-emitting diodes (LEDs). The Aktilite lamp, specifically designed for use with Metvix cream, has an emission spectrum that closely matches the red light absorption profile of PpIX.