Clinical toxicity of interferons in cancer patients: a review

All major types of human interferons (IFNs) have been purified and clinically administered as antitumor agents. We summarize here experience to date with toxicity of IFNs in cancer patients. The acute syndrome consists of fever, chills, myalgias, arthralgias, and headache, with some variation according to type of IFN, route of administration, schedule, and dose. Fatigue, perhaps reflecting CNS toxicity, is the most prevalent nonacute symptom. At high doses, IFNs are neurotoxic; the abnormalities seen by EEG resemble those in diffuse encephalitis. Hematologic toxicity consists mainly of leukopenia, but anemia and thrombocytopenia occur in some patients. Nausea, vomiting, and diarrhea are the main gastrointestinal symptoms. Elevation of serum transaminases seems to reflect liver toxicity. Renal function is well preserved, except for rare instances of acute renal failure. Cardiac toxicity remains questionable, although heart failure and arrhythmias have been associated with the administration of IFNs. Most, if not all, of these effects are reversible or can be ameliorated. With IFN alpha, the type most widely used in clinical studies, doses of 1 million to 9 million units (MU) are generally well tolerated, but doses greater than or equal to 18 MU yield moderate to severe toxicity. Doses greater than or equal to 36 MU can induce severe toxicity and significantly alter the performance status of the patient.