Lack of response in nine patients with breast cancer treated with fibroblast interferon.

Nine patients with metastatic breast cancer were treated with a minimum of 6 X 10(6) U/day of beta-interferon (IFN-beta) for at least 6 weeks. In patients whose disease did not progress during this period treatment was continued to a maximum of 13 weeks, while in other patients doses were escalated. With daily treatments over 3 weeks the maximum tolerated dose was found to be around 60 X 10(6) U/day. Fever occurred regularly. The dose-limiting toxicities were granulocytopenia and increasing liver enzymes. No objective remissions were observed. One patient showed stable disease after her cancer en cuirasse had rapidly progressed under chemotherapy. One patient each with nasopharyngeal carcinoma and fibrous sarcoma were also treated without success. IFN-beta at this moderately toxic dose given over a period of 6-13 weeks is of no clinical value in the treatment of metastatic breast cancer in women.