Beta-interferon, retinoids and tamoxifen in metastatic breast cancer: long-term follow-up of a phase II study.

Based on a series of in vitro data, including the additive and/or synergistic antiproliferative effect of interferon and tamoxifen on breast cancer cell lines, and on clinical reports, we designed a pilot phase II study to test the activity and toxicity of simultaneous administration of beta-interferon (beta-IFN), retinoids (R) and tamoxifen (TAM) as a salvage therapy in a group of patients with metastatic breast cancer (MBC). Herein we describe the outcome of this cohort of patients after a median follow-up of 150 months. Sixty-five stage IV breast cancer patients, 13 pre-treated with hormones, 38 with chemotherapy and 15 with both, received, as a salvage therapy, TAM, beta-IFN and R. Among 65 evaluable patients, 36 achieved a clinical response (55.5%) (95% c.i. 42-67.7%). Toxicity was moderate and mainly hepatic. Median progression-free and overall survival, which did not show any statistically significant difference in patients with different estrogen and progesterone receptor content, were 43 months and 47.9 months, respectively. In conclusion, the study shows that long-term treatment with TAM, beta-IFN and R in MBC is feasible, has moderate toxicity and seems to give a long-term benefit, irrespective of the receptorial status.