Mesothelioma Photodynamic Therapy

Mesothelioma is a disease with no cure at present. A significant amount of research is being conducted in this area. A leading curative methodology is what is known as PDT that was introduced by German physician Friedrich Meyer–Betz in 1913. The method of using laser light to kill mesothelioma cells is called Photodynamic therapy (PDT). Approved by FDA for use in the treatment of non–small cell lung cancer and cancer of the esophagus, photodynamic therapy is still in a nascent stage with regard to mesothelioma treatment. As such, PDT may be classified as an emerging treatment option for the future.

Photodynamic Therapy works in the following manner

• The patient is injected with a photosensitizing agent or photosensitizer. This type of drug makes the cancer cells sensitive to light of specific wavelengths.
• The photosensitizer highlights the cancerous cells. This is achieved either by not collecting in the healthy cells of the body or being eliminated more quickly from the healthy cells and remaining longer in the cancer cells. The specific action depends on the type of drug administered.
• Fiber–optic cables are introduced into the body through open–chest surgery. These cables focus light of just the right frequency on the tumor.
• The above action kills the cancer cell with the help of the toxic molecule that is created by the reaction of the photosensitizer to oxygen.

The advantage of this method of treatment is that the effect of PDT can be localized; the surrounding tissue is not affected as light can penetrate only up to one third of an inch (1 cm) of tissue. This is also a much cheaper alternative to radiotherapy or surgical operation. Post operative recovery is also quick and typically spans hours or days rather than weeks in hospital.

Mesothelioma clinical trials with Photodynamic Therapy has indicated that the method may be used along with mesothelioma surgery to achieve the following benefits:

• To prevent return of mesothelioma cancer in the pleura or lining of the lungs
• To minimize the extent of pleurectomy or removal of the lung or its part in some patients and to avoid the more invasive extrapleural pneumonectomy or removal of the lung and the pleural lining in others.

The drug used as the photosensitizer is Foscan (meta–tetrahydroxyphenylchlorin, mTHPC). Clinical trials are being done to make Foscan safe for use in mesothelioma treatment and to arrive at the correct dosage. Related side effects like skin wounds and sensitivity to light after the treatment would also be learned after repeated studies. Also current are studies on photodynamic therapy in mesothelioma cancer using the photosensitizer drug called porfimer sodium. This mesothelioma drug is commonly used in photodynamic treatment of non–small cell lung cancer of the bronchi.