Clinical applications of photodynamic therapy.

Photodynamic therapy is a modality for the treatment of malignant disease in which a photosensitive drug is selectively absorbed or retained by malignant tissues, after intravenous injection and is then photoactivated by light of an appropriate wavelength, often produced by a laser. Over the past two decades, the combination of haematoporphyrin derivative (HPD) and then its active component dihaematoprophyrin ether (DHE), now marketed as Photofrin, plus red light at 630 nm have been used in clinical practice for the treatment of a range of tumours; some very promising results have been obtained. Several countries have approved this drug/light combination for clinical use for a number of tumours. Some second generation photosensitising agents with appropriate light sources, and with perceived advantages over Photofrin, are under investigation, and it is to be hoped that major improvements in drug/light combinations will enable photodynamic therapy to achieve its full potential in the not-too-distant future.