Procalcitonin: A New Biomarker for Medullary Thyroid Cancer? A Systematic Review.

Medullary thyroid cancer (MTC) is a rare but aggressive thyroid malignancy. The gold-standard biomarker for its diagnosis and follow-up is calcitonin (CT); however, it has a variable half-life dependent on its circadian variability. It has been suggested that a more stable hormone, procalcitonin (PCT), may overcome these problems and its introduction to routine practice may give more accurate results in the diagnosis and follow-up of MTC. We systematically reviewed Pubmed, Scopus, Biosis Previews and Embase databases up to March 2016. A total of 15 out of 184 articles were retrieved and analyzed. Of these 15 studies, 3 were case reports. In these 15 studies, the values of CT and PCT were assessed in both patients with MTC and patients that were either healthy volunteers or with benign/malignant thyroid nodular disease or with bacterial infection. Our search suggests that PCT seems to be a useful biomarker for the diagnosis and follow-up of MTC when used in conjunction with CT, particularly in a small proportion of tumors that are CT-negative or secrete low levels of CT. So far, there has not been enough data to suggest a specific threshold for normal PCT. However, most studies indicate a value of 0.1 ng/ml as an acceptable cut-off in everyday clinical practice. At present, CT should continue to be the primary biomarker in MTC with the addition of PCT in some patient groups. Nevertheless, larger patient series need to be conducted in order to provide safer and more accurate results.