Leukocyte interferon-induced tumor regression in human metastatic breast cancer, multiple myeloma, and malignant lymphoma.

Thirty-eight patients with advanced breast cancer, multiple myeloma, and malignant lymphoma were treated with partially purified (about 0.1%) leukocyte interferon. Patients were treated with a remission-induction schedule of 3 million to 9 million antiviral units daily intramuscularly for 4 to 26 weeks. Responding patients were maintained on a schedule of 3 million U three times weekly. Tumor regression was observed in seven of 17 patients with breast cancer. Six of 10 patients with multiple myeloma responded with a decrease of at least 50% in serum myeloma protein levels or Bence Jones protein excretion. Six of the 11 lymphoma patients achieved tumor regression. Complete remissions occurred in two patients. Of the 19 responding patients, five remain on study for 52 to 63 weeks. Toxicity included low-grade fever, fatigue, anorexia, and partial alopecia. Myelosuppression (lowest median leukocyte count, 2500/mm3; granulocytes, 1300/mm3) occurred in most patients. On the basis of this pilot study, we conclude that leukocyte interferon can induce tumor regression in patients with advanced cancer.