More on Photodynamic therapy

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Photodynamic therapy: discriminating between healthy and cancerous tissue

Charles Spangler, Mikhail Drobizhev, Aleksander Rebane, and Jean Starkey

New two-photon–activated porphyrin designs allow specific, noninvasive targeting of subcutaneous tumors several centimeters below the skin surface.

Photodynamic therapy (PDT) is a noninvasive technique in which specific compounds, termed photosensitizers, are introduced into the bloodstream and subsequently incorporated into tissues throughout the body. Application of a specific wavelength of light can discreetly activate these compounds, leading to cell death in the area of treatment. This approach has considerable potential as an aggressive cancer treatment without the side effects associated with traditional radiation and chemotherapies. Until recently, however, direct treatment of tumors deeper than a few millimeters below the skin surface has remained problematic with the use of currently FDA-approved PDT photosensitizers. In addition, these therapeutic agents often do not adequately discriminate between healthy tissue and tumor cells and can continue to reside in healthy tissue for several days or weeks following treatment, sometimes leading to severe sunlight sensitivity.

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