Does successful interferon treatment of tumor patients require life-long treatment?

Case histories of 5 tumor patients treated with natural leukocyte interferon-alpha (IFN-alpha) are presented. One patient with juvenile laryngeal papillomatosis responded well to interferon treatment, but the disease recurred when therapy was withdrawn. Upon reinstitution of treatment, the patient once again responded well. Another patient with myelomatosis also responded well to interferon therapy and in this case, too, the tumor recurred when interferon treatment was withdrawn. Reinstitution of interferon therapy was, however, unsuccessful. One patient with generalized giant cell tumor of bone responded with regression after more than 5 years of interferon treatment. Another patient with pulmonary osteosarcoma metastases, having received irradiation and interferon combination therapy followed by sole interferon treatment, responded well with a lasting stationary radiogram after 6 years of interferon treatment. One patient with malignant glioma, showing signs of tumor growth during the first few months of interferon therapy, eventually responded, and became disease-free after 6 years. The latter 3 patients are continuously receiving interferon therapy although more than 5 years have elapsed since their interferon therapy was initiated. It is suggested that interferon therapy for malignant tumors be given for life (or to progression of disease) in responding patients. Such a concept entails biological implications for interferon therapy in general and for antitumor action of interferons in particular. Other possible clinical schedules should only be constructed within the framework of controlled clinical trials.