Recombinant DNA human interferon alpha 2 in advanced breast cancer: a phase 2 trial

Effectiveness of recombinant DNA (rDNA) human interferon alpha 2 (IFN alpha 2) in advanced breast cancer was evaluated in 14 patients who had received prior endocrine and/or cytotoxic therapy. After randomization, 7 patients received IFN alpha 2 two million IU m-2 day-1, s.c., 3 times a week (schedule 1) and 7 patients received 50 million IU m-2 day-1, i.v., for 5 consecutive days, every 3 weeks (schedule 2). Treatment duration was 4-21 weeks in schedule 1 and 6-24 weeks (2-8 courses) in schedule 2. Regressions were not achieved with either schedule. Treatment was associated with significant toxicity and was more severe in schedule 2. Dose limiting toxicities were leukopenia, elevation of liver enzymes, hyperglycemia and fatigue. Serum IFN activity was low or undetectable in patients on schedule 1 and high in patients on schedule 2. At 24 h, serum IFN activity was detectable in only 1/6 patients on schedule 1 as compared to 3/7 patients on schedule 2. IFN neutralizing factors were detected in the serum of only 1 patient prior to treatment but none were detected in any of the patients during or after discontinuation of treatment (4-24 weeks). IFN alpha 2 increased the expression of both HLA class 1 antigens and beta 2 microglobulin in peripheral blood lymphocytes in vivo. This effect was dose related.