Mesothelioma Treatment Using Photodynamic Therapy and Surgery

Mesothelioma Treatment

Mesothelioma Treatment: Photodynamic Therapy Is the Subject of Clinical Trials

Photodynamic therapy or PDT uses laser light to kill cancer cells. The Food and Drug Administration (FDA) has approved its use for non–small cell lung cancer and cancer of the esophagus. However, photodynamic therapy is in the early experimental stages as a possible mesothelioma treatment.

How Photodynamic Therapy Works

The patient receives a photosensitizing agent or photosensitizer, which is a drug that makes the cancer cells vulnerable and sensitive to light of specific wavelengths. The photosensitizer collects in the cancerous cells. Depending upon its type, the photosensitizer either does not collect in the healthy cells or is eliminated from these cells more rapidly than from the cancer cells.

After the cancer cells have been sensitized, fiber–optic cables are placed in the body (usually through open–chest surgery) in order to focus light of just the right frequency on the tumor. This causes the photosensitizer to react with oxygen to produce a toxic molecule that kills the cancer cell.

Mesothelioma Clinical Trials Using Photodynamic Therapy

Photodynamic therapy has been used on an experimental basis during surgery to help prevent the recurrence of mesothelioma cancer in the lining of the lungs or pleura. In one clinical trial of 26 patients, photodynamic therapy was combined with either of two types of surgery—a pleurectomy or an extrapleural pneumonectomy (Ann Thorac Surg. 2003 Mar; 75(3): 952–9). A pleurectomy is the removal of lining of the lung or pleura. The more extensive extrapleural pneumonectomy involves removal of both the lung and pleura. The photosensitizer was Foscan (meta–tetrahydroxyphenylchlorin, mTHPC).

The clinical trial sought to establish a safe dose of Foscan and determine side effects. These included skin wounds as well as sensitivity to light some time after treatment. More studies must be done before concluding that Foscan and photodynamic therapy would be a useful and safe mesothelioma treatment.

The researchers pointed out that the use of photodynamic therapy might allow some patients to undergo a lung–sparing pleurectomy rather than the more invasive extrapleural pneumonectomy. Currently, other studies are exploring the interaction of surgery and photodynamic therapy using the photosensitizer porfimer sodium, a drug commonly used in photodynamic treatment of non–small cell lung cancer that affects the bronchi.