Immunotherapy is an experimental form of biotherapy that uses the body’s own disease-fighting mechanism, the immune system, to fight cancer. It can be used alone, but more often it is used in conjunction with another type of therapy to increase the effectiveness of that treatment.
In intrapleural immunotherapy, agents that stimulate the immune system are inserted directly into the chest cavity. This procedure seems to improve the average survival rate in mesothelioma patients that have large amounts of white blood cells that have infiltrated the tumor according to a study titled The scientific basis for the immunotherapy of human malignant mesothelioma, published in 1993 in the European Respiratory Review.
Interleukin-2, also known as IL-2, is used in immunotherapy. It’s a cytokine, a protein molecule secreted by immune system cells whose job is to regulate the immune system. It isn’t the direct cause of tumor cell death. It stimulates the growth of other immune cells called T-Cells and Natural Killer Cells that get rid of the cancer cells.
T-Cells work by identifying the antigen or protein associated with an individual tumor cell. The body contains many types of T-Cells, but each one only recognizes one specific antigen. Natural Killer Cells attack tumor cells also. However, they don’t need to recognize an antigen in order to attack, which is way they are called natural killers.
In a study titled Intrapleural administration of interleukin-2 for the treatment of patients with malignant pleural mesothelioma, published November 15, 1998 in Cancer, researchers studied 22 patients with malignant mesothelioma who were given IL-2 for five days without interruption or reduction in dose amount. Three patients had Stage IA disease, one had Stage IB, 16 had Stage II, one had Stage III, and one had Stage IV.
The researchers found that there were 11 partial responses and one complete response. The disease stabilized in three patients and progressed in seven patients. The average survival time overall was 18 months; however, the average survival time of responders was 28 months as compared with eight months for non-responders. The 24- month survival rate for responders was 58 percent and the 36-month survival rate for responders was 41percent.
The second agent used in this type of therapy is gamma-interferon, a protein made by T-Cells that prevents viruses from reproducing. However, it has not been shown to be as effective as IL-2.
In a study titled Activity of intrapleural recombinant gamma-interferon in malignant mesothelioma, published April 15, 1991 in Cancer, researchers studied 22 patients with malignant pleural mesothelioma, 12 of whom were classified as Stage I and 10 of whom were Stage II, who were given gamma-interferon twice a week over two months. They observed that of the 19 patients that could be evaluated, four complete responses and one partial response were observed in Stage I patients. One partial response was observed in Stage II patients.
The study titled Intrapleural treatment with recombinant gamma-interferon in early stage malignant pleural mesothelioma, published November 1, 1994 in Cancer showed better results. However, all patients in the study were either Stage I or Stage II, and this was only a Phase II clinical trial. Eighty-nine patients were given gamma-interferon twice a week for eight weeks. There were eight complete responses and nine partial responses with at least a 50 percent reduction in tumor size. The overall response rate was 20 percent. The response rate for patients with Stage I disease was 45 percent.
Colony-stimulating factors, like granulocyte-macrophage colony-stimulating factor (GM-CSF), are also substances that can trigger an antitumor immune response; and they are being tested to see if they are effective as immunotherapy agents. GM-CSF is another cytokine, or protein produced by immune cells that stimulates the production of two types of white blood cells, granulocytes and macrophages. Researchers at the University of Western Australia have conducted clinical trials using the patient’s own tumor in vaccines with GMCSF.