Exemestane and anastrozole yielded similar survival outcomes as first-line therapy in a cohort of women with breast cancer, according to study findings.
The open-label, randomized, phase 3 trial included 7,576 women with hormone-dependent postmenopausal breast cancer who received 5 years of therapy with exemestane or anastrozole.
EFS served as the primary endpoint. Secondary endpoints included OS, distant DFS, incidence of contralateral new primary breast cancer and safety. The method of analysis was two-sided test of superiority to detect 2.4% improvement with exemestane.
The median patient age at enrollment was 64.1 years. The median follow-up duration was 4.1 years.
By median follow-up, 4-year EFS was 91% among the exemestane group and 91.2% among the anastrozole group (stratified HR=1.02; 95% CI, 0.87-1.18).
Researchers reported similar outcomes between the two drugs regarding OS, distant DFS and disease-specific survival.
Discontinuation due to adverse events, concomitant disease or study refusal occurred in 31.6% of patients. Other findings from the adverse event profile indicated that osteoporosis/osteopenia, hypertriglyceridemia, vaginal bleeding and hypercholesterolemia occurred less frequently in the exemestane cohort, and mild liver function abnormalities and rare episodes of atrial fibrillation were less frequent in the anastrozole cohort. Both drugs were associated with similar rates of vasomotor and musculoskeletal symptoms.
“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 researchers concluded.
The reduced bone toxicity reflects previous hypotheses, and exemestane may be considered as an option for adjuvant therapy in this patient population, they added.