Innovative Mesothelioma Therapies

Traditional cancer treatment regimens such as radiation and chemotherapy are widely used for mesothelioma patients, but they do not offer a cure for the disease. Increasingly, patients have turned to unconventional forms of therapy in the hope that the answer lies with gene therapy, immunotherapy or photodynamic therapy. All of these treatment options should be discussed with the patient’s physician prior to setting out on a course of alternative treatment.

Gene Therapy

Gene therapy is a method for correcting defective genes that cause disease development. The therapy can work in several ways. Scientists can correct defective genes by removing, inserting, replacing, or altering genes in order to treat or prevent a disease.

To treat a disease such as mesothelioma, a carrier called a ‘vector’ would be used to deliver the therapeutic gene. Generally, viruses are used because they already have the capacity to invade a cell. Also, viruses are very good at targeting specific cells. In gene therapy, viral vectors are changed so they do not create a new virus in the cell, but just drop off a new gene.

Many scientists are searching for ‘suicide genes’ that would attack cancer cells, while leaving normal cells untouched. Gene therapy is a fairly new treatment approach, still very much in the experimental stages, and cannot be administered without the patient’s participation in a clinical trial.

Immunotherapy

Immunotherapy is also known as biological therapy, biotherapy, or biological response modifier (BRM) therapy. It is a treatment designed to stimulate the body’s own natural immune defenses to stop the spread of cancer. Scientists have determined that the immune system can recognize and eliminate cancer cells under some circumstances. The problem with mesothelioma is that the body does not recognize the cancer cells as abnormal.

Immunotherapy uses BRMs to boost the body’s natural ability to fight disease. Interferons, interleukins, tumor necrosis factors, monoclonal antibodies and cancer vaccines are all BRMs. Some occur naturally in the body, and others are generated synthetically in the lab. BRMs seem to change the body’s relationship with mesothelioma cells, so the body recognizes them as abnormal. As a result, the body’s ‘immune response’ kicks in to attack the mesothelioma cells and prevent the cancer from growing. Immunotherapy also seeks to block the process by which mesothelioma alters a normal cell into a cancer cell. Scientists hope that BRMs can stop the migration of mesothelioma to other parts of the body, and prevent its further growth.

Preliminary studies have demonstrated considerable shrinkage of tumors at very early stages of mesothelioma. But more research is required to determine whether immunotherapy will be effective as a mesothelioma treatment. In Phase I and Phase II clinical trials of a combined immunotherapeutic and chemotherapeutic approach for mesothelioma patients, the results failed to show any meaningful effect on survival or relapse rate.

Photodynamic Therapy

Photodynamic therapy (PDT) uses a drug that is activated by light and applies laser light to it. The two work together to target and destroy cancer cells while keeping damage to surrounding healthy tissue at a minimum. The therapy begins with the patient’s injection with a non-toxic photosensitizer drug. The drug invades all cells of the body, but in about two days, normal cells excrete the drug. Then the patient is exposed to laser light, which will activate the drug remaining in the cancer cells and destroy them. Timing is critical, because the tumor cells must be exposed to the laser light after the drug is excreted by the normal cells, but before the drug is expelled by the mesothelioma cells.

It is unclear what role photodynamic therapy may play in the treatment of mesothelioma. Since the laser light cannot be absorbed at any great depth in the body, treatment via PDT can only be used on superficial areas of the body. Still, the treatment may be ideal for the treatment of mesothelioma after surgical removal of the tumor. Some doctors have applied PDT intraoperatively after surgery, but the number of patients treated in clinical trials is small, making it difficult to draw definitive conclusions. Most reports concerning PDT are Phase I and II studies and the only phase III study was conducted with an earlier generation photosensitizer. That study reported no advantage in using PDT in combination with surgery and immunochemotherapy. At present, all that is known is that PDT can be performed safely with newer generation photosensitizers and that results are encouraging for mesothelioma patients with stages I and II disease.