Estracyt in advanced carcinoma of the breast: a phase II study.

Estracyt, a conjugate of an alkylating agent with an oestrogenic sterol, was given in a dose of 420 mg daily to a group of 44 postmenopausal patients with very advanced breast carcinoma. Thirty-eight of these were in relapse following chemotherapy and 32 had evidence of distant metastases. Seventeen patients had an objective response and marked or complete alleviation of symptoms, four others had a useful symptomatic response but no beneficial effect was observed in the remainder. Three who had shown no response to previous oestrogen therapy also failed to respond to Estracyt as did all nine patients with hepatic metastases. Oestrogen receptor status and age within the postmenopausal group seemed to have no bearing on the result. Side-effects were minimal with nausea in 18 patients but in only two did this necessitate withdrawal of the drug. Bone marrow depression did not occur. Changes in acute-phase reactant proteins suggested that part of the Estracyt was de-esterified in the liver liberating oestrone but the low incidence of vaginal haemorrhage and the recalcification of bony metastases suggested that on the whole Estracyt behaves as an anti-oestrogen as well as an antimitotic.