Interferon therapy in multiple myeloma.

A woman with multiple myeloma relapsed after 6 years of satisfactory tumor control with melphalan therapy. When progression then occurred, she was given exogenous human leukocyte interferon, 3 x 10(6) reference units twice daily i.m., as the sole therapy. Side-effects of the interferon therapy consisted of fever reactions and thrombocytopenia. One month after the initiation of interferon therapy there was 1) improvement of general health with less pain and tiredness, 2) reduction of the M-component, IgG-lambda, in the serum, and 3) a reduced plasma cell concentration in the bone marrow. After 5 months of interferon therapy tumor progression occurred despite continuous interferon treatment. At the same time, the tumor cells were less sensitive to interferon in in vitro tests than prior to interferon therapy. It is suggested that interferon therapy should be given as initial treatment to a few patients with multiple myeloma in a phase I trial.