Role of serum cytokeratin 19 fragment (Cyfra 21.1) as a prognostic biomarker in patients with differentiated thyroid cancer.

Differentiated thyroid cancers (DTC) account for up to 85% of thyroid cancers and generally display an excellent prognosis. However, in a minority of cases, DTC progress toward less differentiated phenotypes leading to distant metastases and even disease-related deaths. Circulating biomarkers are warranted to complement the gold standard DTC marker thyroglobulin (Tg) in identifying and monitoring such cases. We measured serum Tg and Cyfra 21.1 6 to 12 months after primary treatment in 473 DTC patients. A complete response of Tg was related to an excellent outcome in all cases. Among patients with incomplete Tg response Cyfra 21.1 levels <2.07 ng/mL were associated to favorable outcome while higher levels greatly increased the risk of disease related recurrences and deaths. Both markers retained independent prognostic values in multivariate analysis. In conclusion, Cyfra 21.1 is a tool available to independently predict survival of DTC patients not achieving excellent response after primary treatment.