OP19 – The Utility of the Calcitonin (Ctn) to Carcinoembryogenic Antigen (CEA) Ratio in Prognostication of Medullary Thyroid Carcinoma (MTC)

      Jaber, Tania1; Milton, Denái2; Grubbs, Elizabeth G3; Trotter, Chardria S3; Zafereo, Mark4; Cabanillas, Maria E1; Dadu, Ramona1; Cote, Gilbert J1; Hu, Mimi I1 1 Endocrine Neoplasia and Hormonal Disorders, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 2 Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 3 Department of Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 4 Head and Neck Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX, USA   Background/Purpose: Ctn and CEA doubling times (DTs) are established measures to predict outcomes for MTC patients. However, DTs require multiple values over years for validity. The objective of this study was to evaluate whether an instantaneous Ctn to CEA ratio (CCR) is predictive of outcome. Methods: We reviewed the charts of 210 MTC patients who were seen at our institution between 2003 and 2016. CCRs were calculated preoperatively and at 3-9 months postoperatively (nadir). Post-operative cure was defined as an undetectable Ctn and a CEA within the normal range at their post-operative nadir. Results: The median follow-up time was 54.4(0-378) months after initial surgery. The median overall survival was 190.5 (95% CI,143-229) months. 38 (19%) patients had distant disease at presentation. A higher pre-operative CCR was associated with a lower likelihood of post-operative cure (odds ratio [OR]: 0.70 [0.53-0.91]; p=0.009), with a ratio over 16 being most predictive of no cure (OR:0.30 [0.13-0.70]; p=0.006). A higher nadir CCR was associated with need for systemic therapy (OR:1.57 [1.15-2.13]; p=0.004) and with death from MTC (OR:1.67 [1.15-2.41], p=0.007), with a median nadir CCR of 52.2 and 71.1 in the two groups, respectively. Discussion/Conclusion: To our knowledge, this is the only study evaluating the CCR as a predictor of post-operative outcome. Our study suggests that the pre-operative CCR can predict post-operative cure, and that the nadir CCR is predictive of treatment with systemic therapy and with death from MTC. Clinicians can use this prognostic measure to counsel patients early on in their cancer diagnosis.   References: Meijer JA, le Cessie S, van den Hout WB, Kievit J, Schoones JW, Romijn JA, Smit JW. Calcitonin and carcinoembryonic antigen doubling times as prognostic factors in medullary thyroid carcinoma: a structured meta-analysis. Clin Endocrinol (Oxf). 2010 Apr;72(4):534-42.


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