Photodynamic therapy: the clinical perspective. Review on applications for control of diverse tumorous and non-tumorous diseases.

Photodynamic therapy (PDT) is an innovative and attractive modality for the treatment of small and superficial tumours. PDT, as a multi-modality treatment procedure, needs both, a photosensitizer with distinct tumour selectivity and a powerful light source that matches the absorption spectrum of the photosensitizer. The purified haematoporphyrin derivative Photofrin is so far the only sensitizer approved for phase III/IV clinical trials. Major drawbacks of this product are: lack of chemical homogeneity, skin phototoxicity, unfavourable physicochemical properties and poor selectivity in terms of uptake and retention by tumour versus normal cells. Most second generation photosensitizers, including the phthalocyanines, show an increased photodynamic efficiency in the treatment of animal tumours and reduced phototoxic side effects. In 1997, there were more than half a dozen new sensitizers in or about to start clinical trials. To introduce the basic principles of photodynamic therapy, the current review article discusses in some more detail the treatment of endobronchial lung cancer, one of the leading indications of PDT. Moreover, a broad overview is given on the use of PDT for treatment of a wide variety of tumorous and nontumorous diseases, including new strategies for control of rheumatoid arthritis and application of PDT for extracorporeal bone marrow purging.