Clinical use of biologic response modifiers in cancer treatment: an overview. Part I. The interferons.
Interferons are proteins with antiviral, antiproliferative, and immune-regulating activity. They are classified as alfa, beta, or gamma on the basis of antigenicity and biologic properties. Alfa interferons as single-agent therapy produce clinical improvement in approximately 90 percent of patients with hairy-cell leukemia, and up to 70 percent of patients with chronic myelogenous leukemia (CML) in early-stage disease. Prolonged suppression or elimination of the leukemic cell clone by interferon may ultimately increase survival of patients with CML. Interferon is not effective single-agent therapy for multiple myeloma, but improves response rate when combined with conventional agents. AIDS-associated Kaposi's sarcoma demonstrates a 40 percent objective response rate to interferon, with less risk of immune system suppression than conventional cytotoxics. Other applications of alfa interferon include malignant melanoma and renal cell carcinoma. Beta interferon is similar to the alfa subtype and may have utility in treatment of brain tumors. Gamma interferon is an important immune regulator with qualitative and quantitative differences in its efficacy and toxicity when compared with alfa interferon.