Photodynamic Therapy Expands Its Horizons

Extract

Photodynamic therapy—the use of light to fight cancer—is poised to take on a more prominent role in oncology 20 years after the first major studies of the treatment began.

In December 1995, the U.S. Food and Drug Administration granted its first PDT approval to QLT Photo- Therapeutics of Vancouver, B.C., Canada, to market the light-sensitizing drug Photofrin (porfimer sodium) for the treatment of obstructive esophageal cancer.

Like most of the settings in which researchers have studied PDT, the FDA approved use is a palliative treatment for patients with advanced cancer. But experts say PDT may prove useful in treating a wide range of cancers, from early to late stages. PDT also holds promise for treating other diseases ranging from psoriasis to macular degeneration of the retina, the most common cause of blindness in the elderly.

The primary ingredients in PDT are low-energy lasers and photosensitizing drugs such as Photofrin that make cells vulnerable to damage by light. Photofrin is a semi-synthetic compound derived from the blood of cows and pigs, while some newer photosensitizers are totally synthesized.