Diagnostic value of selected biochemical markers in the detection of recurrence of medullary thyroid cancer - comparison of calcitonin, procalcitonin, chromogranin A, and carcinoembryonic antigen.

INTRODUCTION: Medullary thyroid cancer (MTC) is a malignancy of the thyroid gland, which derives from parafollicular C cells. Periodic measurement of biochemical markers of MTC remains a crucial part of patient follow-up and disease monitoring. The aim of the study was to compare the diagnostic value of four selected markers - calcitonin (Ct), procalcitonin (PCT), chromogranin A (CgA), and carcinoembryonic antigen (CEA).

MATERIAL AND METHODS: Patients with histopathologically confirmed MTC hospitalised in a single department between January 2015 and December 2015 were included in the study. Patients were subdivided into two groups: a remission group and an active disease group, based upon serum markers of MTC and imaging. Levels of Ct, PCT, CgA, and CEA were compared between the groups.

RESULTS: Forty-four patients were included; 20 patients presented active disease and 24 were in remission. All patients with active disease had Ct exceeding the upper limit of normal range (10 pg/mL) - for that threshold the sensitivity was 100.0% and the specificity was 73.9%; for the best-fit threshold of 121.0 pg/mL the specificity was 95.8% with sensitivity 100.0%. There was significant correlation between Ct and PCT - p < 0.000001, r = 0.93. All patients with active disease exceeded the upper limit of the normal range (0.5 ng/mL) - for that threshold the sensitivity was 100.0% and the specificity was 83.3%; for the best-fit threshold of 0.95 ng/mL the specificity was 95.8% with sensitivity 100.0%. In case of CEA for the best-fit threshold of 12.66 ng/mL the specificity was 100.0% with sensitivity 57.9%; for CgA the best-fit threshold was 75.66 ng/mL with specificity 83.3% and sensitivity 75.0%.

CONCLUSIONS: Our study confirms that PCT can be considered as an equivalent alternative for measurement of calcitonin. On the other hand, it is also worth noting that MTC can be a rare cause of very high levels of PTC not resulting from infectious diseases. The diagnostic value of CEA and chromogranin A is much lower and can be within the normal range even in patients with advanced, metastatic MTC. They should be used only as accessory markers.