Clinical and immunological study of beta interferon by intramuscular route in patients with metastatic breast cancer.

Partially purified human beta interferon (HuIFN-beta) was administered to six patients with metastatic breast carcinoma by the intramuscular route at doses of 3 X 10(6) and 6 X 10(6) units on a daily schedule. Objective antitumor effects were observed in three patients (one partial remission, two minor responses) in soft tissue and lymph node metastases. Systemic side effects (fatigue, fever, pruritus, nausea, etc.) attributable to the treatment occurred in all patients. Augmenting effects by IFN-beta on cell-mediated immunity in vivo (delayed-type hypersensitivity) and in vitro natural killer cell and antibody-dependent cell-mediated cytotoxicity were observed in several patients. The clinical and immunological effects were considered evidence of systemic biological activity despite very low or undetectable serum antiviral activity following administration of this agent.