Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
Fareston (Schering-Plough)
60 mg tablets
Indication: breast cancer
Tamoxifen is an anti-oestrogen with a well-established role in breast cancer. Toremifene has a similar structure and can be used as an alternative to tamoxifen in the treatment of postmenopausal women with hormone-dependent breast cancer.
The antitumour effect is mainly due to toremifene binding to oestrogen receptors. This inhibits the oestrogen-induced stimulation of cell replication.
Toremifene is taken once daily. It is quickly absorbed and food does not have a significant effect on the extent of absorption. Toremifene is almost totally bound to albumin. There is extensive metabolism and an active metabolite is produced. The metabolites are mainly excreted in the faeces. As the half-life of toremifene is long, it takes 4-6 weeks for the concentration to reach a steady state.
Toremifene and tamoxifen have been compared in 3 main trials. In terms of response and survival, the two drugs were generally equivalent.
Some of the adverse effects of toremifene can be expected because of its mechanism of action. Common adverse effects include hot flushes, leucorrhoea, oedema, nausea and vomiting.
Approximately 3% of the women in clinical trials had to withdraw due to adverse reactions. There is a risk of hypercalcaemia in the first week of treatment, particularly if the patient has bony metastases. There is insufficient evidence to determine if toremifene shares the potential of tamoxifen to increase the risk of endometrial cancer during long-term treatment. So far, toremifene appears to have no clear advantage over tamoxifen.
