Tumors that have spread to the liver or lungs (visceral
metastases) are associated with a worse prognosis than
tumors in soft tissue and bone only. Here we review available efficacy data to address whether or not
anastrozole, a non-steroidal
aromatase inhibitor (AI), is effective in postmenopausal patients with advanced
breast cancer (ABC) and visceral
metastases. We include data from Phase III clinical trials, comparing clinical benefit (CB) with
anastrozole versus
tamoxifen as a first-line treatment, and versus
megestrol acetate (MA) or
fulvestrant as a second-line
therapy. Patients in these trials had adequate organ function and the volume of disease had to be minimal or moderate for them to be eligible for inclusion. First-line treatment of patients with or without visceral
metastases in the overall population resulted in CB rates of 49.5 and 62.3%, respectively, for
anastrozole and 46.9 and 55.9%, respectively, for
tamoxifen. In patients with confirmed
hormone receptor (HR)-positive
tumors, the CB rate was 51.9 and 65.7%, respectively, for
anastrozole and 41.6 and 58.7%, respectively, for
tamoxifen. In patients with or without visceral
metastases, second-line treatment with
anastrozole resulted in a CB rate of 31.4 and 51.8%, respectively, compared with 31.9 and 47.1%, respectively, for those treated with MA. Patients in the overall population with and without visceral
metastases treated with
anastrozole obtained a CB rate of 37.4 and 43.8%, respectively, while those treated with
fulvestrant obtained a CB rate of 38.2 and 47.6%, respectively. In patients with confirmed HR-positive
tumors, CB was seen in 37.6 and 41.5%, respectively, of patients treated with
anastrozole and in 37.3 and 47.0%, respectively, of patients treated with
fulvestrant. The results reveal
anastrozole to be an effective and valuable first- and second-line
therapy in postmenopausal women with ABC and visceral
metastases, showing similar CB to other endocrine
therapies.