Hormone replacement therapy as treatment of breast cancer--a phase II study of Org OD 14 (tibilone).

Org OD 14 (tibilone) is a synthetic steroid, designed to combine the favourable effects of oestrogens, progestagens and androgens into a single substance for use as hormone replacement therapy (HRT). Given its antiovulatory properties, the ability to control menopausal symptoms and blocking action on progesterone receptors, Org OD 14 was considered as an agent with potential anti-cancer activity while at the same time helping existing menopausal symptoms. In this phase II study, 14 post-menopausal women with advanced or metastatic breast cancer, who had failed on tamoxifen, were treated with Org OD 14. The median duration of treatment was 12 weeks and all patients stopped because of progressive disease with or without toxicity. Vaginal bleeding occurred in four patients, three of whom had recently stopped tamoxifen. One response was seen: an 82-year-old patient had a partial response in an axillary soft tissue mass, improvement in liver function tests and an improvement in her performance status that lasted over 6 months. One patient with progressive disease on Org OD 14 improved on stopping the drug. In view of the vaginal bleeding, Org OD 14 should not be given to patients who have recently stopped tamoxifen.