Staging and Treatment
Interferons are natural substances produced by the normal cells of most body tissues in response to viral infections and disease. Manufactured forms of interferons have been shown to help the body's immune system fight disease more effectively. There are three general types of interferons that are used to treat human diseases, interferon alfa, interferon beta, and interferon gamma. To date only interferon alfa has been found to be useful in treating cancer.
The immune system enables the body to distinguish cells that are native to the body from those cells and sub-cellular organisims that are foreign. These foreign invaders include viruses, bacteria, and other disease-causing organisms.
The body recognizes foreign, diseased, or cancerous cells by special marker substances known as antigens on their surfaces. These markers allow your body's immune system to distinguish abnormal or foreign cells from healthy cells in the tissues of your body. When this occurs, the immune response sends an array of immune cells to contain and destroy or wall off the foreign or cancerous invading cells.
Cells of the body's immune system that have been stimulated or recognized antigens against which they are targeted will begin to produce interferons and other natural immune signalling substances. These substances not only combat foreign invaders, which may cause infection, they can also prevent the growth and spread of other diseased cells, including cancer.
One type of interferon, interferon alfa-2b, has been shown in two randomized prospective trials to prolong disease-free and overall survival in patients with high-risk melanoma. These results led to the U.S. Food and Drug Administration approval of interferon alfa-2b as adjuvant therapy for melanoma in 1996.
In other studies, high dose interferon produced promising results in terms of delaying relapse in stage II patients, while little if any benefit was seen in high-risk patients.
Clinical trials are currently underway to further evaluate whether the highly significant benefit of high-dose interferon given for a full year can be duplicated with the treatment given for only one month, or a new form of long-acting less toxic (PEG) interferon given weekly for many years. Other promising approaches may include melanoma vaccines or combinations of interferon with other forms of immunotherapy, such as interleukin-2. For more information about some other adjuvant therapies in clinical trial, see the section, Experimental Therapy.
Interferon therapy cannot be administered orally because strong acids and enzymes in our digestive systems would destroy it. Therefore, interferon must be delivered directly into the blood stream or into tissue. In the first phase of interferon therapy, called the induction phase, interferon is administered to the patient intravenously. This may be done in a hospital or in an office setting. The induction phase generally involves five days of interferon therapy per week for a four-week period. Each subcutaneous injection should take about twenty to thirty minutes.
The second phase of interferon therapy, called the subcutaneous injection maintenance phase, begins in the fifth week and involves three injections per week. This routine continues for the remainder of the year. During this phase many patients and their loved ones learn to administer the injections of interferon themselves.
Interferon Side Effects
As with any treatment, the side effects of interferon therapy depend on the prescribed dose. In addition, all people differ in their individual responses to therapy. Thus, some patients will have many side effects, while others may have none at all. Often, patients experience the most side effects during the first few weeks of therapy. After this period, many patients find that their side effects diminish greatly. Many patients tolerate low dose therapy very well, while high-dose interferon therapy tends to produce more severe and consistent side effects.
The main side effects of interferon therapy are fatigue and flu-like symptoms. Flu-like symptoms include fever, chills, headache, and general body aches. Another common symptom is loss of appetite. Diminished appetite can sometimes be attributed to feelings of nausea or the development of a metallic taste in the mouth. Less common side effects include mild hair thinning, dry itchy skin, palpitations, and lightheadedness. If side effects are severe, you should inform your doctor about and ask about all possible solutions.
Some laboratory tests may become abnormal with high-dose interferon including blood counts (5%), liver enzymes (14%) and kidney and thyroid function (> 10%).
These side effects are generally reversible when therapy is stopped. If the symptoms or signs are significantly abnormal, the treatment may be interrupted for a time, and then resumed at a lower dose. Throughout the course of the therapy, treatment may be stopped and restarted at different dosages as needed.