Presence of Circulating Tumor Cells in High-Risk Early Breast Cancer During Follow-Up and Prognosis

Abstract

The prognostic relevance of circulating tumor cells (CTCs) at the time of primary diagnosis has been well established. However, little information is available regarding their prognostic relevance to follow-up care. The multicenter, open-label, phase III SUCCESS A trial compared two adjuvant chemotherapy regimens followed by 2 vs 5 years of zoledronate for early-stage, high-risk breast cancer patients. The presence of CTCs was assessed before and 2 years after chemotherapy using the FDA-approved CellSearch System. Overall survival (OS) and disease-free survival (DFS) were analyzed using univariate log-rank tests and multivariable Cox regressions. OS and DFS were measured starting from an assessment of CTCs 2 years after the completion of chemotherapy. All statistical tests were two-sided. The sample included 1087 patients who participated in the translational research program of the SUCCESS A trial and for whom sufficient translational data were available regarding CTC status at baseline and at the 2-year follow-up visit. Two years after chemotherapy, 198 (18.2%) patients were CTC-positive. The median follow-up after this timepoint was 37 months. Cox regressions that included CTC status at baseline revealed that CTC status 2 years after chemotherapy had statistically significant and independent prognostic relevance for OS (hazard ratio [HR] = 3.91, 95% confidence interval [CI] = 2.04 to 7.52, P < .001) and DFS (HR = 2.31, 95% CI = 1.50 to 3.55, P < .001). The presence of CTCs 2 years after chemotherapy was associated with decreased OS and DFS. Based on these results, active individualized surveillance strategies for breast cancer survivors based on biomarkers should be reconsidered.