Advanced breast cancer updates on anastrozole versus tamoxifen

Abstract

Results from two studies, the North American trial and the Tamoxifen or Arimidex Randomized Group Efficacy and Tolerability (TARGET) trial carried out in Europe/rest of the world comparing 'Arimidex' (anastrozole) 1 mg with tamoxifen 20 mg for treatment of advanced breast cancer in postmenopausal women, have previously been reported individually and as a prospectively combined analysis. For the combined analysis, at a median follow-up of 18.2 months anastrozole was shown to be superior to tamoxifen in terms of time to progression (TTP; P=0.022) in the hormone receptor-positive subgroup. Both treatments were well tolerated; anastrozole was associated with significantly fewer thromboembolic events (P=0.043) and fewer reports of vaginal bleeding. The survival analyses and safety update in the overall population and in the hormone receptor-positive subgroup from the combined data are now available. At a median follow-up of 43 months, 56.0% of patients in the anastrozole group and 56.1% of patients in the tamoxifen group had died. At the cut-off date, 2-year mortality rates were 31.7 and 32.5% with anastrozole and tamoxifen, respectively, in the overall population. Median time to death (TTD) was similar for both treatments (39 months versus 40 months, respectively; hazard ratio (HR) 0.97, lower 95% confidence limit (CL) 0.84). Similar findings were reported in the hormone receptor-positive population. With longer follow-up, both anastrozole and tamoxifen remained well tolerated. Sequencing data showed that patients crossed from anastrozole to tamoxifen or tamoxifen to anastrozole are similar regarding efficacy. In conclusion, these TTP, survival and tolerability data support the use of anastrozole as a first-line therapy of choice in postmenopausal women with advanced breast cancer.