Prognostic significance of early circulating tumor DNA during treatment of ER+/HER2- advanced breast cancer

Patients with advanced estrogen receptor-positive, HER2-negative (ER+/HER2-) breast cancer commonly develop resistance to treatment with hormone therapy and CDK4/6 inhibitors. Responders cannot be distinguished from non-responders after the first cycle of treatment under current practice. A post-hoc ancillary study of the French phase 3 PADA-1 trial assessed cicrulating tumor DNA measures at early time points as prognostic markers in ER+/HER2- advanced breast cancer. The study found that early on-treatment evolution of ctDNA was prognostic for both PFS and OS. A ctDNA-based risk model improved survival discrimination over traditional RECIST and clinical parameters.