Phase II trial of recombinant beta (IFN-betaser) interferon in the treatment of metastatic breast cancer.

Nine patients with metastatic breast cancer received 30 x 10(6) I.U. of Interferon - Betaser (Betaseron) intravenously daily times five for two consecutive weeks followed by a two week rest period. Only one patient received more than one such cycle of Betaseron. The drug was well tolerated in eight of these patients. One patient, with liver metastases and liver dysfunction, developed hepatic decompensation during therapy. Toxicity consisted of anorexia, chills, fever, fatigue and nausea with an occasional patient having emesis. One patient developed severe thrombocytopenia, two, significant leukopenia and nine, mild elevations of serum transaminase. Two patients developed beta interferon binding antibodies but none developed neutralizing antibodies. No anti-tumor responses were seen and disease progression occurred rapidly during the four week cycle in eight of nine patients.