Distant metastasis of papillary thyroid cancer (PTC) is a multistep and complex process that frequently complicates the disease with poor prognosis. The presence of circulating tumor cells (CTCs) in the peripheral blood has been reported in several cancer types to be highly related to the development of distant metastasis. Nevertheless, the CTCs status during the progression of PTC is rarely investigated. This study aimed to define and compare the CTCs counts among the healthy control individuals (Group I, n = 14), the PTC patients in disease-free status (Group II, n = 9), and the patients with distant metastasis (Group III, n = 8). The patients in group III had metastases to the lung and mediastinum (n = 4), bones (n = 3), and lung and kidney (n = 1), respectively. CTCs were enriched from the peripheral blood by the negative selection method PowerMag that has been validated in our previous study. CTCs enumeration was performed by immunofluorescence staining using the anti-epithelial cell adhesion molecule (EpCAM) and anti-thyroid stimulating hormone receptor (TSHR) antibodies. The EpCAM+ and TSHR+ CTCs counts were 2.97 ± 2.03 and 9.97 ± 9.22 cells/mL for group I, 10.43 ± 9.03 and 19.17 ± 9.77 cells/mL for group II, and 100.06 ± 73.34 and 141.60 ± 82.08 cells/mL for group III individuals, respectively (p < 0.01). These data indicate that (1) some of the TSHR+-CTCs are not EpCAM+ and this type of cell population can be overlooked if CTCs were enriched by the method based on positive selection of EpCAM+ cells; (2) the PTC patients in disease-free status has higher CTCs counts than the healthy control individuals and, hence, continuous CTCs enumeration is recommended for the patient in the stage of disease-free; (3) the PTC patients with distant metastases have higher CTCs counts when compares to the healthy control subjects and the patients with disease-free status. In conclusion, CTCs enumeration is thereby warranted in the course of diagnosis and treatment of thyroid cancer.

Citation Format: Hung-Chih Lin, Ju-Chien Cheng, Ching-Ping Tseng, Jen-Der Lin. Distinct levels of circulating tumor cell counts for the papillary thyroid cancer patients with distant metastases and in disease-free status. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2097. doi:10.1158/1538-7445.AM2014-2097