Francois-Clement Bidard, MD, PhD, professor, medical oncologist, Institut Curie, discusses the clinical utility of circulating tumor cell count (CTC) in breast cancer at the 2018 San Antonio Breast Cancer Symposium.

CTC count was found to be a useful method of selecting frontline treatment for patients with estrogen receptor—positive, HER2-negative metastatic breast cancer. Data presented from the phase III STIC CTC trial revealed that CTC count can be used to guide treatment decisions in terms of hormone therapy and chemotherapy. In the trial, 778 patients were randomized 1:1 to a physician’s choice hormone therapy or chemotherapy arm or to a CTC-guided treatment arm.

The study met its primary endpoint of CTC-driven noninferiority. Patients whose treatment was adjusted to chemotherapy based on CTC count had a 5-month extension in median progression-free survival versus patients in the physician’s choice arm. Moreover, overall survival was 37.1 months compared with 42 months in the physician’s choice and CTC-driven arms, respectively.

Because the trial was conducted prior to the introduction of CDK4/6 inhibitors, it should only serve to guide treatment decisions between frontline hormone therapy and chemotherapy. Nonetheless, this research suggests that CTC count can be used as a prognostic biomarker in this setting and may lead to improved survival.

Francois-Clement Bidard, MD, PhD

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Dr. Bidard on the Clinical Utility of Circulating Tumor Cell Count in Breast Cancer