Effects of fulvestrant 750mg in premenopausal women with oestrogen-receptor-positive primary breast cancer.

Fulvestrant (Faslodex) is a pure anti-oestrogen that reduces markers of hormone sensitivity and proliferation in postmenopausal women with oestrogen-receptor (ER)-positive breast cancer. This randomised trial compared the effects on the tumours of a single dose of 750mg fulvestrant to those of daily tamoxifen (20mg) taken 14-16 days prior to surgery in 60 premenopausal women with ER-positive primary breast cancer. There were statistically significant falls in the expression of ER and Ki67 levels compared to the baseline with both drugs. Both drugs caused a decrease in PgR expression from baseline but this was only statistically significant with fulvestrant. No statistically significant differences were seen between the two treatment groups. Fulvestrant caused an increase in circulating levels of oestradiol, irrespective of the stage of the menstrual cycle at which patients commenced treatment. No major changes were seen in LH, FSH and progesterone levels with either drug. The most common adverse events with fulvestrant were headaches, hot flushes, nausea and disturbance of menses. Contrary to previous studies with fulvestrant 250mg, these findings suggest that at a dose of 750mg fulvestrant is effective at reducing the effects of oestrogen on ER-positive breast cancer in premenopausal women.