Skin cancer, photodynamic therapy

Phototherapy is the generic term covering therapies which use light either with or without a sensitiser. Those that do not require a sensitiser use the natural chromophores within the tissue to perform this function e.g. treatment of vitamin D deficiency in rickets, and neonatal jaundice). Those that do use an added sensitiser include photochemotherapy (largely psoriasis and skin disorders) and photodynamic therapy (currently mainly cancer). Photodynamic therapy is differentiated from photochemotherapy by its additional requirement for the presence of oxygen at molecular or ambient levels.In this text we will deal only with photodynamic therapy since, at the present time, this is the main driving force in phototherapy. ° ... 

Porphyrins 21 are the backbone of major players in life cycles—cytochromes (Scheme 8). There are three types of cytochromes, classified by their color, or more precisely by their long-wavelength absorption band, as a (600 mn), b (563 nm), and c (550 nm). They are protein conjugates of a porphyrin complex with iron(II), which is a coenzyme called heme (22). In plants, porphyrins form a complex with magnesium-(II) chlorophylls a and b (23), vital in photosynthesis. Porphyrin derivatives are used in photodynamic therapy for dermatological diseases such as psoriasis, and for skin or subcutaneous cancer.5c-e... 

Work during the last ten years on photodynamic therapy (PDT) has established the methodology as effective in the early treatment of cancers, and in the treattnent of certain skin disorders and viral infections. Approval by the regulatory authorities for sensitisers in this process began in 1993 when Canada allowed the use of Photofrin (QLT Therapeutics), an action followed later by most countries around the world. Now many other companies have sensitisers at late stage clinical dials (2001), see below in Table 4.5. An excellent introduction to the chemistry of this topic is provided in the book written by Bonnett. ... 

Kendall, C. A. and Morton, C. A. (2003). Photodynamic therapy for the treatment of skin disease Technology in Cancer Research Treatment 2 283-288. 

Third, since a chemical reaction induced by multibeam irradiation only proceeds at the position where both beams overlap, a chemical process induced by multibeam irradiation is a site-selective process. This third advantage is important in photodynamic therapy, in which damage to healthy cells must be avoided. One of the most advanced techniques is to perform selective damage of cancer tissues deep beneath the skin surface (Fig. 2.4). Molecular memory is also possible when taking this feature into account. Because various reactive... 

DeRosa, F.S., Marchetti, J.M., Thomazini, J.A., Tedesco, A.C., and Bentley, M.V. (2000) A vehicle for photodynamic therapy of skin cancer influence of dimethylsulphoxide on 5-aminolevuhnic acid in vitro cutaneous permeation and in vivo protoporphyrin IX accumulation determined by confocal microscopy, J. Control Release, 65 359-366. 

Verteporfin is a second-generation photosensitizer developed for photodynamic therapy of eye diseases, non-melanoma skin cancer and psoriasis [30]. It is constituted as a mixture of the two regio-isomeric dihydrobenzoporphyrine acids 39/40 obtained from non-selective hydrolysis of the corresponding (synthetic) tetraester. 

R. Fink-Puches, H.P. Soyer, A. Hofer, H. Kerl, P. Wolf (1998). Long-term followup and histological changes of superficial nonmelanoma skin cancers treated with topical delta-aminolevulinic acid photodynamic therapy. Arch. Dermatol., 134, 821-826. 

F. Cairnduff, M.R. Stringer, E.J. Hudson, D.V. Ash, S.B. Brown (1994). Superficial photodynamic therapy with topical 5-aminolevulinic acid for superficial primary and secondary skin cancer. Br. J. Cancer, 69, 605-608. 

D.G. Pennington, M. Waner, A. Knox (1988). Photodynamic therapy for multiple skin cancers. Plast. Reconstr. Surg., 82, 1067-1071. 

Photodynamic therapy (PDT) is dedicated to the treatment of cancerous and noncancerous skin lesions (such as head, neck, etc.) by activating injected photosensitisers (Seim et al., 2007). 

Attili, S.K., et al., 2009. An open pilot study of ambulatoiy photodynamic therapy using a wearable low-irradiance organic light-emitting diode light source in the treatment of nonmelanoma skin cancer. British Journal of Dermatology 161 (1), 170—173. 

---