The role of circulating tumor cells as a prognostic marker in the adjuvant setting of patients with breast cancer

Background Still, there is no clinically reliable marker to detect micrometastasis or breast cancer relapse. This study aimed to evaluate the role of circulating tumor cells (CTCs) as a biomarker in patients with nonmetastatic breast cancer. Patients and methods CTC quantification was carried out using flow cytometry for 50 patients with breast cancer postoperatively: before starting, after three cycles, and at the end of adjuvant chemotherapy. The relationship between CTCs and other tumor characteristics and outcomes were studied. Results The median follow‑up duration was 35 months. Before starting adjuvant chemotherapy, CTCs were positive (cutoff point ≥5/7.5 ml) in 36% of the patients and decreased to 20% after finishing chemotherapy (P = 0.04). CTCs were detected in 88.9% (n = 16 of 18) of node‑positive patients and in 11.1% of node‑negative patients (n = 2 of 18, P = 0.04). No significant association was found with tumor size, grading, or hormone receptor status. Distant metastasis was detected in 20% (n = 10 of 50) of patients and was significantly associated with CTCs more than or equal to 5 in 80% of them (n = 8 of 10) (P = 0.01). The presence of more than or equal to 5 CTCs at baseline was associated with a reduction in both the disease‑free survival and overall survival (P 0.001 and P = 0.003, respectively). Baseline CTCs more than or equal to 5/7.5 ml were confirmed as an independent prognostic factor in multivariate Cox hazard regression analysis for disease‑free survival (hazard ratio = 3.71; 95% confidence interval = 1.62–8.48; P = 0.002) and overall survival (hazard ratio = 3.14; 95% confidence interval = 1.34–7.37; P = 0.009). Conclusions The current work suggested that the presence of more than or equal to 5 CTCs/7.5 ml at baseline would predict early disease recurrence and reduce the overall survival in patients with nonmetastatic breast cancer receiving adjuvant chemotherapy.