Importance: Our understanding of the utility of circulating tumor cells (CTCs) and disseminated tumor cells (DTCs) as clinical biomarkers continues to evolve.
Objective: This study evaluated (1) clinicopathologic factors associated with the presence of CTCs or DTCs, (2) the prognostic value of CTCs or DTCs by disease stage, 3), the value of these biomarkers in predicting the benefit of chemotherapy.
Design: This is a retrospective analysis of patients with breast cancer (BC) diagnosed between 2004 and 2016 using the National Cancer Database (NCDB). To evaluate variables associated with the presence of CTCs or DTCs at the univariate level, we used chi-squared and Wilcoxon rank-sum tests. Multivariate logistic regression models were then constructed using significant variables. Consequently, we included CTC or DTC status (i.e. positive or negative) in multivariate, stage-by-stage Cox regression analyses for overall survival (OS). After stratifying by receptor status and staging, we used the Kaplan-Meier method to explore chemotherapy efficacy in CTC- or DTC-positive vs. CTC- or DTC-negative subsets.
Results: Factors significantly associated with CTCs were race, progesterone receptor status, HER2 status, histology and AJCC N- and M-staging. Factors associated with DTCs were race, HER2 status, histology and AJCC N-staging. CTCs were associated with poor OS in late-stage (III and IV) but not early-stage (0-II) BC. DTCs were not significantly associated with OS in either context. In hormone receptor (HR)-positive disease, chemotherapy was associated with better OS when CTC status was positive, both in early-stage and late-stage disease. In a subset of patients without CTCs, however, chemotherapy conferred no survival benefit. DTC status was not a significant predictor of chemotherapy efficacy in early or late-stage, HR+ disease.
Conclusions: This study suggests that CTC-status is a significant prognostic factor at later stages of BC; yet it can also help guide management of early-stage disease as it appears predictive for chemotherapy benefit.
Keywords: biomarker; cancer treatment; chemotherapy; circulating tumor cells; survival.