This study was undertaken to evaluate serum cytokeratin 19 fragment (Cyfra 21.1) expressions in patients with advanced thyroid carcinoma and to explore the relationship between serum Cyfra 21.1 and the degree of radioiodine ((131)I) avidity of thyroid carcinoma cells.
Enrolled were 76 consecutive patients with advanced thyroid carcinoma submitted to high-activity (131)I treatment. In each patient, serum thyroglobulin (Tg) and Cyfra 21.1 were measured before (131)I administration and compared with the posttreatment whole-body scan results.
Thirty-one (41%) of 76 patients had iodine-avid and 45 (59%) had iodine-refractory diseases respectively. Significantly higher serum Cyfra 21.1, but not Tg, levels were found in patients with (131)I-refractory disease compared with patients with iodine-avid disease (P<0.01).
This is the first report describing the potential role of serum Cyfra 21.1 as marker of dedifferentiation and resistance to (131)I therapy in patients with advanced thyroid carcinoma.