Circulating tumor cell status and benefit of radiotherapy in stage I breast cancer.

Abstract

11524 Background: Circulating tumor cell (CTC) status has been shown to be prognostic of decreased survival in non-metastatic breast cancer. While up to 20-30% of patients with early breast cancer have detectable CTCs, less is known regarding the role of CTC-status in guiding clinical management. Methods: An observational cohort study was performed on women with stage I breast cancer evaluated for CTCs from the 2004-2014 National Cancer Database. Logistic regression was used to explore clinicopathological associations with CTC-status. Kaplan-Meier and multivariable Cox proportional-hazards survival analyses were used to estimate associations of CTC-status with overall survival using a propensity score-adjusted and inverse probability-weighted matched cohort. Results: Of the stage I breast cancer women evaluated for CTCs, 23.1% (325/1,407) were CTC-positive. Age, histology, receptor status, and nodal stage were associated with CTC-status. CTC-status was an effect modifier of the radiotherapy-survival association: CTC-positive women who did not receive radiotherapy had an increased hazard of death compared to CTC-negative women who also did not receive radiotherapy (four-year survival: 85.7% vs. 93.3%, HR = 2.92, CI = 1.43-5.98, P = 0.003). CTC-positive patients treated with radiotherapy did not have decreased survival compared to CTC-negative patients not treated with radiotherapy (HR = 0.67, CI = 0.28-1.65, P = 0.40). From the matched cohort analysis, CTC-positive women who did not receive radiation had a 4.82-fold increased hazard of death compared to CTC-positive women treated with radiotherapy (four-year survival: 83.2% vs. 96.6%; CI = 2.62-8.85, P < 0.001). Conclusions: Treatment with adjuvant radiotherapy was associated with improved survival in CTC-positive women with stage I breast cancer. If prospectively validated, CTC-status may be valuable as a predictor of benefit of radiotherapy in early stage breast cancer.