Abstract
BACKGROUND: Serum tumour markers, cancer antigen 15-3 (CA 15-3) and carcinoembryonic antigen (CEA) are not routinely recommended for detecting breast cancer recurrence and monitoring treatment. In this study, we aim to evaluate the diagnostic accuracy of absolute CA 15-3 and CEA levels and report on the clinical utility of tumour marker velocity in breast cancer surveillance. METHODS: 67 consecutive patients over a 15-year period (1998-2012) with available serial serum CA 15-3 and CEA measurements at recurrence were matched to a control group of patients. Tumour marker velocity was derived from the average change in consecutive tumour marker values over time, expressed in unit/year. Logistic regression analysis was performed to investigate the association between tumour characteristics, tumour marker velocity and disease recurrence. RESULTS: Using the Youden index values, the optimal cut-off values for absolute CA 15-3 and CEA corresponded to the normal assay reference range while tumour marker velocity values were derived to be 2.5U/mL/year and 1.2ng/mL/year respectively. CA 15-3 velocity > 2.5U/mL/year had the highest AUROC value of 0.85 than CEA velocity alone. When either tumour marker velocity exceeded threshold values, the sensitivity, specificity, negative predictive value and positive predictive value were 94.0%, 73.1%, 92.5%, and 77.8% respectively. In the multivariate logistic regression analysis, having both CA 15-3 and CEA velocity exceeding the cut-off values was shown to be a significant predictor for disease recurrence (p = 0.01). CONCLUSION: These findings highlighted the clinical utility of serial tumour markers measurements and its velocity in breast cancer surveillance.