Photodynamic therapy (PDT), also called photoradiation therapy, phototherapy, or photochemotherapy, is a treatment that combines a light source and a photosensitizing agent (a drug that is activated by light) to destroy cancer cells. It has been approved by the United States Food and Drug Administration (FDA) for certain cases of cancer of the esophagus and non-small cell lung cancer (NSCLC), and was most recently approved to treat actinic keratosis, a precancerous skin condition.
PDT works because the photosensitizing agent collects more readily in cancer cells than in normal cells. When the agent is then exposed to light, it reacts with oxygen to create chemicals that can kill the cell. Because the approved light sources can only penetrate a limited depth through tissue, PDT is mainly used to treat areas on or just under the skin, or in the lining of internal organs.
Clinical trials have shown that PDT can be as effective as surgery or radiation therapy in treating certain kinds of cancers and precancerous conditions, and has potentially fewer side effects. Another possible advantage is that therapy can be repeated several times at the same site if necessary.
How Long Has It Been Available?
In December 1995, the FDA approved a photosensitizing agent called porfimer sodium (Photofrin) combined with light from a laser for treating patients with cancer of the esophagus in the following situations:
- To relieve symptoms of esophageal cancer, including difficulty swallowing, that are caused by a tumor obstructing (blocking) the esophagus
- To treat esophageal cancer that cannot be treated with laser therapy alone
In 1998, the FDA approved porfimer sodium for two additional uses:
- To treat endobronchial (affecting the lining of the bronchi) non-small cell lung cancer that is microinvasive (has minimal spread of cancer cells) for patients who cannot have other types of treatment such as surgery or radiation therapy
- To reduce obstruction and to palliate (ease) symptoms in people with endobronchial non-small cell lung cancer that is either completely or partially obstructing the bronchi
Aminolevulinic acid (Levulan Kerastick), a topical solution, received approval in December 1999 to treat actinic keratosis, a precancerous skin condition that is caused by excessive sun exposure. This product has only been approved for use on the face or scalp. A blue light (BLU-U Blue Light Photodynamic Therapy Illuminator) is used rather than light from a laser.