Findings from SONIA, a phase III Dutch study comparing "the sequence of an aromatase inhibitor plus CDK4/6 inhibitor as first-line treatment followed by fulvestrant as second-line treatment (CDK4/6 inhibitor first-line group") did not improve overall survival compared with second-line treatment. Rather, this treatment regimen increased treatment-related and financial toxic effects in patients with HR-positive HER-2 negative advanced breast cancer. Following an analysis of 1050 patients enrolled in SONIA, median overall survival was 47.9 months with first-line CDK4/6 inhibitor and 48.1 months with second-line CDK4/6 inhibitor
To learn more about the SONIA study, click here.
Sources mentioned:
- Wortelboer N, van Ommen-Nijhof A, Konings IR, et al. Overall Survival With First-Line vs Second-Line CDK4/6 Inhibitor Use in Advanced Breast Cancer A Randomized Clinical Trial JAMA Oncology; Published online 19 February 2026. doi: 10.1001/jamaoncol.2025.6585
- Valenza C, Burstein HJ. Lessons From the SONIA Trial on Timing of CDK4/6 Inhibitors in Advanced Breast Cancer—The Sooner, the Better? JAMA Oncology; Published online 19 February 2026. doi: 10.1001/jamaoncol.2025.6345
