Key clinical point: Circulating tumor cell (CTC) counts may be a reliable biomarker for guiding the choice of first-line treatment in patients with hormone receptor–positive, HER2-negative metastatic breast cancer.

Major finding: The median progression-free survival was similar whether CTC counts or clinical factors were used to guide treatment choice. The median progression-free survival was 15.5 months in the CTC arm and 13.9 months in the standard arm, which meant the primary endpoint for noninferiority was met (hazard ratio, 0.94; 90% confidence interval, 0.81-1.09).

Study details: A phase 3 trial of 755 patients with hormone receptor–positive, HER2-negative metastatic breast cancer.

Disclosures: The study was funded by the Institut Curie, the French National Cancer Institute, and Menarini Silicon Biosystems, the maker of the CTC assay used in the trial. The investigators disclosed relationships with Menarini and many other companies.