Serum Carcinoembryonic Antigen as a Biomarker for Medullary Thyroid Cancer

ABSTRACT

Background and Objectives@#The lack of known elevated biomarkers in cancer surveillance is a challenge for diagnostics. However, few studies have assessed the proportion of patients with medullary thyroid cancer (MTC) that presented with elevated serum carcinoembryonic antigen (CEA) level. @*Materials and Methods@#This was a retrospective study of 115 patients treated for MTC at Samsung Medical Center between 1995 and 2017. Serum calcitonin and CEA levels that were available at one of the following time points were included (a) within 3 months before the initial surgery, (b) when a structural recurrence was confined to the neck, or (c) when a distant metastasis was identified during follow-up. Considering the high false-positive rate of serum CEA testing, 5 ng/mL was selected as the cut-off threshold. @*Results@#The sensitivity of CEA at the time of diagnosis was 54%, but it significantly increased with anatomical stage, from 20% in stage I to 88% in stage IV (p for trend ＜0.001). At the time of diagnosis, larger tumor size, more frequent gross extra-thyroidal extension, more frequent N1b, and a higher number of metastatic lymph nodes were significantly observed in CEA-positive patients compared with CEA-negative patients (p＜0.05). The sensitivity of CEA at the time of recurrence was 56% for local recurrence and 80% for distant recurrence. @*Conclusion@#The CEA value was associated with anatomical stage as a biomarker for MTC and could be used to predict poor prognosis. However, serum CEA testing plays a limited role in diagnosis and follow-up of MTC because it can show normal values even in advanced disease.