A phase III open-label trial of exemestane vs anastrozole in postmenopausal women with hormone-dependent early breast cancer found that both agents produced similar median rates of event-free survival—91% for exemestane and 91.2% for anastrozole—as well as similar distant disease-free and disease-specific survival.
“This first comparison of steroidal and nonsteroidal classes of aromatase inhibitors showed neither to be superior in terms of breast cancer outcomes as 5-year initial adjuvant therapy for postmenopausal breast cancer by two-way test,” the investigators from the NCIC Clinical Trials Group (NCIC CTG) MA.27 reported in the Journal of Clinical Oncology. “Exemestane should now be considered another safe and effective option in addition to anastrozole or letrozole as initial adjuvant therapy for patients with hormone receptor–positive postmenopausal breast cancer,” the researchers concluded.
The multicenter, multinational study enrolled 7,576 women with a median age of 64.1 years. All had histologically confirmed, adequately excised, primary invasive breast cancer. “Compliance was poor, with a 31.6% discontinuation rate (33.8% and 29.4% in exemestane and anastrozole groups, respectively) for adverse effects, concomitant diseases, or study refusal,” the authors noted.
The investigators found no evidence of differences in menopausal-like symptoms between the two treatment groups, although adverse effects differed. “Osteoporosis/osteopenia, hypertriglyceridemia, vaginal bleeding, and hypercholesterolemia were less frequent on exemestane, whereas mild liver function abnormalities and rare episodes of atrial fibrillation were less frequent on anastrozole. Vasomotor and musculoskeletal symptoms were similar between arms,” the investigators stated.
The effects of exemestane on bone health will be investigated more fully in the group’s bone substudy. ■
Goss PE, et al: J Clin Oncol 31:1398-1404, 2013.