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Tamoxifen and its principle metabolite N-desmethyltamoxifen can modulate multi-drug resistance in vitro. Tamoxifen 480 mg/day was given for 6 days with oral etoposide on days 4-6 to 17 patients with advanced solid tumours. Venous thrombosis (2 patients), reversible neurological toxicity (1 patient), and WHO grade III nausea/vomiting (3 patients) related to tamoxifen were observed but overall toxicity was manageable. One partial response occurred in 15 assessable patients. Mean plasma concentrations of tamoxifen and N-desmethyltamoxifen increased to 4.3 mumol/l and 2.7 mumol/l, respectively, by day 6. Plasma concentrations corresponding to active in vitro levels were attained by most patients.

The endocrine and therapeutic effects of the luteinising hormone-releasing hormone (LHRH) analogue, Zoladex, have been assessed in 28 postmenopausal women with advanced breast cancer. Fourteen had responded to previous hormone therapy and 14 had received no previous hormone therapy. Zoladex treatment resulted in 2 partial responses and 2 patients with stable disease for more than 6 months in the former group, and 1 partial response and 2 with stable disease for more than 6 months in the latter group. Toxicity was minimal. All responses occurred in soft tissue disease. Peripheral oestradiol levels fell after 1 month of Zoladex from 33 pmol/l (+/- 20 SD) to 22 pmol/l (+/- 11 SD) (p less than 0.005) and both responders and nonresponders showed similar changes in oestradiol. Oestrone levels did not change significantly. Six out of 7 patients who received tamoxifen after progression of disease on Zoladex, showed a response. These results suggest that Zoladex acts indirectly via changes in peripheral hormone levels rather than directly on LHRH receptors on the tumour.

In the postmenopausal woman, low plasma oestrogen levels are due to the cessation of ovarian follicular activity, and residual oestrogen is thought to result from the adrenal glands and ovaries, both sources of androgens for peripheral oestrogen synthesis. In a study of 21 postmenopausal women with advanced breast cancer, Zoladex (goserelin), 3.6 mg depot, monthly, had no affect on the adrenal-derived androgens, but a direct effect on ovarian secretion of androgens is thought to have occurred. Thus, in such women, medical adrenalectomy is likely to produce an incomplete suppression of plasma androgens, but its combination with Zoladex may provide a new therapeutic option.