Photodynamic Therapy

Photodynamic therapy (PDT) uses a combination of a photoactive drug (a drug that is activated by light) and light from a laser. Both work by targeting and destroying cancer cells while limiting damage to surrounding healthy tissue. Light therapy starts with an injection of a non-toxic photosensitizer drug. The drug goes into all cells of the body, but normal cells excrete it in about two days. Timing is crucial, because the tumor cells need to be exposed to the laser light after the drug has left the healthy cells but before the drug has left the mesothelioma cells. The laser light will activate the drug present within those cells and destroy them.

The role, if any, for PDT in the treatment of mesothelioma has yet to be established. Because of the limited depth of the absorption of the light, treatment via PDT is limited to superficial areas but may be ideally suited to the treatment of mesothelioma following surgical resection. Limited centers have applied PDT intraoperatively after surgical resection; however, the number of patients treated in the different trials is small, and no definitive conclusions can be drawn. Most reports are Phase I and II studies. The final outcome of these studies with respect to survival is of limited value. The only phase III study, which was performed with an earlier generation photosensitizer, reported no advantage to the use of PDT in combination with surgery and immunochemotherapy.

To date, the most that can be said is that intraoperative PDT with newer generation photosensitizers can be performed safely in experienced centers, and that there are some encouraging results, especially in patients with stages I and II MPM.