Circulating Cell-free DNA in Serum as a Marker for the Early Detection of Tumor Recurrence in Breast Cancer Patients

Background/Aim: Circulating cell-free DNA (cfDNA) isolated from serum by noninvasive procedures can serve as a potential biomarker for the early detection of many cancers. The aim of this study was to implement a simple, yet effective quantitative method for measuring the cfDNA in serum and to investigate the relationship between cfDNA and the occurrence of recurrence in breast cancer (BrCa) patients. Patients and Methods: A total of 240 cases were selected, which comprised different subtypes of BrCa patients and control individuals. We selected 20 serum samples from patients which showed recurrence after 4-7 years of disease-free survival. SYBR green was used as a reporter molecule to estimate the amount of cf DNA in these serum samples. Results: A global Wilcoxon analysis was performed to compare the cf DNA abundance between nonrecurrent and recurrent patients. The amount of cf DNA was higher in recurrent patients (recurrent vs. non-recurrent ratio=1.3; p=0.03; AUC=0.76) compared to non-recurrent patients. The data between normal/healthy controls and nonrecurrent patients indicated no significant differences (n=20 in each group, healthy to non-recurrent ratio=1.03; p=0.20; AUC=0.61). Conclusion: We implemented a straightforward one-step technique to measure the amount of cf DNA in serum, which can translate into a clinical diagnostic tool in the near future. The high levels of cf DNA in the serum of recurrent BrCa patients compared to non-recurrent BrCa patients indicates a possible uncovered role for circulating genetic information, which either contributes to the cancer recurrence phenomenon or at the very least, serves as an identifier for the potential of recurrence.