Like interferons, interleukins are cytokines, naturally produced proteins of the immune system. One type, interleukin-2, causes the immune system's T-cells to multiply and perform a variety of functions, including killing cancer cells. Interleukin-2 is also believed to be able to activate anti-tumor cells, such as natural killer cells.

Interleukin-2 may be used as a single agent or in combination with chemotherapy and/or interferon (biochemotherapy). Several studies of combination therapy with interleukin-2 and interferon alpha have been conducted without clear-cut improvement over interleukin-2 alone.

The US Food and Drug Administration (FDA) has approved interleukin-2 for the treatment of advanced, metastatic melanoma. In a study of 270 patients, 16% experienced tumor shrinkage. Tumors disappeared completely in 6% of patients, some of whom continued to be cancer-free without further treatment almost three years later.¹ However, it is not clear whether this long-term survival is the result of treatment or patient selection, since no randomized, controlled trials have been conducted.

High-Dose Interleukin-2

Interleukin-2 must be delivered by injection directly into the bloodstream or into tissue. It cannot be taken orally because the strong acids and enzymes of the digestive system would destroy it.

The FDA-approved regimen involves the intravenous injection of high doses of interleukin-2, administered by an experienced physician. Patients are hospitalized during treatment. The course of treatment occurs in two five-day cycles, in which one dose is injected every eight hours for up to 14 doses. The cycles are separated by a nine-day rest period, during which the patient can go home.

The high dosages have a strong likelihood of lowering blood pressure and causing fluid to leak from blood vessels into tissues and lungs. Patients should be closely monitored immediately following treatment for these potentially life-threatening reactions.