Beta interferon, retinoids and tamoxifen in the treatment of metastatic breast cancer.

Based on the additive or synergistic antiproliferative effect of interferon and tamoxifen on breast cancer cell lines and on preclinical and clinical data on retinoids alone and incombination with antiestrogen or interferon, we designed a pilot phase II study to test the toxicity of simultaneous administration of interferon-beta (IFN-beta), retinoids (R), and tamoxifen (TAM) and the efficacy of this combination as salvage therapy in a group of patients with metastatic breast cancer (MBC), A total of 49 stage IV breast cancer patients, 11 pretreated with hormones, 26 with chemotherapy, and 12 with both, received 30 mg TAM and two dose levels of IFN-beta and retinyl palmitate, Among 49 evaluable patients, 27 achieved a clinical response (55%; 95% CI 41-69%), 10 had stable disease (20%), and in 12 (25%) the disease progressed, Toxicity with both dose levels was moderate and mainly hepatic, Median response duration, not statistically different in estrogen receptor-positive and negative patients, was 31.4 months (range 4.9-67), Median overall survival was 19.2 months (range 2-69), We have shown that long-term administration of TAM, IFN-beta, and retinyl palmitate is feasible with moderate toxicity, We have also demonstrated that this regimen is active in pretreated MBC patients and that responses are not influenced by receptor status.