Purpose: Minimally invasive follicular thyroid carcinomas (MIFCs) are uncommon; literature offers limited guidance on their natural history and management. Starting January 2015 we measured circulating tumor cells (CTCs) in patients with MIFC (n=22) or benign thyroid tumors with follicular features (n=4).
Methods: In a retrospective analysis, we assessed detectability of and serial changes in CTC, compared demographic/clinical differences between CTC-positive versus CTC-negative subgroups using Student's t-test, and examined correlations between CTC status and serum thyroglobulin using Spearman's test. CTCs were quantitated via immunomagnetic separation/microscopic inspection.
Results: Thirteen patients (50%: 12/22 MIFC, 1/4 benign tumor) were initially CTC-positive; 3 remained CTC-positive in ≥1 subsequent measurement. CTC-positive patients had larger tumors and more frequent multifocality and vascular invasion versus CTC-negative patients (n=13). However, no tested variable differed significantly between the subgroups. After 17.2±10.5 months, neither subgroup showed evidence of disease. Significant correlation was absent (p ≥ 0.263) between CTC and Tg negativity (r = 0.243; n=13 evaluable) or initial CTC positivity and Tg positivity (r = -0.418; n=9 evaluable).
Conclusions: In the studied settings, CTC measurement is feasible, has unclear clinical/outcome implications, but may provide different information versus thyroglobulin testing. Lengthier assessment is warranted in larger series.
Keywords: circulating tumor cells (CTCs); differentiated thyroid carcinoma (DTC); minimally invasive follicular thyroid carcinoma (MIFC); risk stratification.