CCND1 Copy Number Variation in Circulating Tumor DNA from Luminal B Breast Cancer Patients

Background/Aim: Abnormalities in the cyclin D1-CDK4/6 complex have been implicated in breast cancer proliferation and resistance to treatment. Recently, new drugs have been developed to target CDK4/6. Meanwhile, liquid biopsy has received great interest in oncology. In this study, we analyzed cyclin D1 gene (CCND1) copy number variation (CNV) in circulating tumor DNA (ctDNA) from luminal B breast cancer patients. Patients and Methods: This study included 31 patients with luminal B breast cancer who underwent resection. We analyzed CCND1 CNV in ctDNA by digital droplet PCR. Results: Of the 31 luminal B breast cancers, CCND1 CNV was positive in 5 cases. Patients with CCND1 CNV positivity had significantly shorter recurrence-free survival than patients with negative CCND1 CNV. Conclusion: CCND1 CNV in ctDNA was associated with poor prognosis in patients with luminal B breast cancer. This biomarker could be a useful prognostic factor.