Everolimus plus aromatase inhibitors as maintenance therapy after first-line chemotherapy: Final results of the phase III randomised MAIN-A (MAINtenance Afinitor) trial

Background: Despite endocrine therapy being the mainstay of treatment for hormone receptor positive (HR+)/HER2-metastatic breast cancer, patients at risk of visceral crisis or doubt for endocrine sensitivity are still offered first-line chemotherapy. Maintenance hormonal therapy is generally offered at the discontinuation of chemotherapy. The MAINtenance Afinitor study is a randomised, phase III trial comparing maintenance everolimus combined with aromatase inhibitors (AIs) versus AI monotherapy in patients with disease control after first-line chemotherapy. Methods: Patients with stable disease, partial response or complete response after first-line chemotherapy were randomised to everolimus plus AIs (exemestane or letrozole or anastrozole) or to AIs alone. Primary aim was progression-free survival (PFS). Secondary aims included response rate, safety and overall survival (OS). Results: In total, 110 patients were randomised to everolimus + AIs (n = 52) or to AIs (n = 58). Median PFS was 11.0 months (95% confidence interval [CI] 8.1-13.8) in the everolimus + AI arm and 7.2 months (95% CI 4.7-10.9) in the AI monotherapy arm (hazard ratio [HR] 0.71, 95% CI 0.47-1.06 ). Objective response rate was 22.4% in everolimus + AI arm and 19.2% in AI monotherapy arm. A higher proportion of disease progression as best response was reported in the AI monotherapy arm (28.8% versus 14.3%). Median OS was 35.7 months (95% CI 26.0-47.8) in the combination arm versus 33.5 (95% CI 26.4-42.7) in the AI alone arm (HR 1.0, 95% CI 0.61-1.62). Conclusions: EVE + AIs did not significantly impact on the outcome of metastatic breast cancer patients deemed suitable for first-line chemotherapy. Also taking into account treatment tolerability, maintenance endocrine therapy remains the standard. Trial registration: EudraCT: 2013-004153-24. 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).