Bisphosphonate-related osteonecrosis of the jaws associated with photodynamic therapy.

Photodynamic therapy (PDT), which is used to manage different solid tumors and many nonmalignant diseases, involves a 2-step process: 1) the selective uptake and retention of a photosensitizer in neoplastic or abnormal tissues; and 2) activation of the photosensitizer with a specific wavelength of nonthermal light, usually from a laser. 1 Hopper C. Photodynamic therapy: A clinical reality in the treatment of cancer. Lancet Oncol. 2000; 1: 212 Abstract Full Text Full Text PDF PubMed Scopus (430) Google Scholar The light activates the photosensitizer, which interacts with molecular oxygen to produce an excited state. This results in the production of oxygen free radicals or the formation of intracellular singlet oxygen, which causes cell death. 2 Henderson B.W. Dougherty T.J. How does photodynamic therapy work?. Photochem Photobiol. 1992; 55: 145 Crossref PubMed Scopus (2199) Google Scholar The direct cytotoxic activity and microvascular damage contribute to the destruction of abnormal/tumor cells, which is manifested as swelling and the formation of necrotic tissue. 3 Biel M.A. Photodynamic therapy in head and neck cancer. Curr Oncol Rep. 2002; 4: 87 Crossref PubMed Scopus (61) Google Scholar Several photosensitizers are used that are classified as first- and second-generation types. The former include porfimer sodium (Photofrin, Aptalis, Canada), 5-aminolevulinic acid, and verteporfin (a benzoporphyrin derivative). A potent second-generation photosensitizer is temoporfin or meta-(tetra-hydroxy-phenyl)chlorine (Foscan; Biolitec Pharma, Edinburgh, Scotland). Temoporfin has the advantage of rapid light activation; it is activated with red light at 652 nm, which penetrates tissue to a depth of 10 mm and has a photosensitivity limited to 2 to 3 weeks. 4 Berenbaum M.C. Akande S.L. Bonnett R. et al. Meso-tetra-(hydroxyphenyl)-porphyrins, a new class of potent tumour photosensitizers with favourable selectivity. Br J Cancer. 1986; 54: 712 Crossref Scopus (192) Google Scholar PDT contraindications include the presence of any form of porphyria or known allergies to porphyrins.