Natural interferon-beta and tamoxifen in hormone-resistant patients with advanced breast cancer.

Tamoxifen (T) is the mainstay of hormonal treatment and is able to give high response rates in selected postmenopausal women with advanced breast cancer (ABC). Nevertheless, even in responders, invariably resistance to hormones is developed. In a previous paper we reported that in a subset of patients (pts) with metastatic breast cancer the resistance to the antiestrogen could be overcome by pretreatment with natural interferon-beta (nIFN-beta) followed by the association of nIFN-beta and T. In the present study we adopted a treatment schedule employing nIFN-beta (3 x 10(6) IU/day im three times a week) and T (60 mg/day) concurrently in 30 pts with ABC progressive to previous treatment with T (30 mg/day). We obtained a 13% response rate with a median duration of response of 8 months (range 4-16 m). All the responses occurred in pts whose disease progressed after an initial response to T. Stabilisation of disease was observed in 37%. Toxicity was mild. In our opinion the use of the combination T plus nIFN-beta in the treatment of breast cancer remains investigational and the optimal scheduling still undetermined.