Photodynamic Therapy

Traditional mesothelioma treatments have been unable to inhibit the growth and spread (metastasis) of the deadly asbestos cancer, requiring the research and develop of new modalities through which to combat the disease. One of the newer modalities currently undergoing clinical trial testing is photodynamic therapy (PDT).

Photodynamic therapy is not limited in its capacity to treat additional cancer types; however, as mesothelioma has thus far proven to be incurable, the asbestos cancer takes precedence over some of the more treatable disease types.

Photodynamic therapy involves the use of a variety of photosensitizing drugs/agents called photosensitizers. Photosensitizers are injected into the bloodstream intravenously where they are absorbed by cells located throughout the body. During the photodynamic therapy process, patients are exposed to a specific wavelength of light. The photosensitizers react to the exposure by producing a type of oxygen that kills nearby cells.

How do photosensitizers differentiate healthy cells for cancerous cells? Simply stated, they don't. Photosensitizers are absorbed by all the body's cells; however, they linger in tumor cells far longer than they do normal cells. Anywhere from 24 hours to 72 hours after the injection of photosensitizers, a tumor is exposed to the specific wavelength of light. Having waited for the photosensitizers to leave most of the normal cells, negative effects are limited; though not wholly uncommon. The photosensitizers that remain in the tumor cells absorb the light and produce a type of oxygen capable of killing the cancerous cells.

In addition to killing cancer cells directly, photodynamic therapy can treat cancer in two other ways:

1. The blood vessels in the tumor can be damaged, preventing cancerous masses from receiving the nutrients required for growth and survival.
2. The immune system can be alerted to attack cancer cells naturally.