BACKGROUND This study aimed to evaluate the recurrence and survival after initial curative-intent surgery of resectable anaplastic thyroid cancer (ATC) and poorly differentiated thyroid cancer (PDTC).

METHODS A retrospective analysis was conducted on patients with ATC and PDTC who had been treated between 1985 and 2013. Among them, 119 patients who had undergone surgery with curative intent were included in this study. The outcome measures included the clinical response to treatment and the recurrence rates of three separate thyroid cancer groups: ATC, differentiated thyroid cancer (DTC) with anaplastic foci, and PDTC.

RESULTS Initial remission was achieved in 100 (84.0%) patients, with higher percentages in patients with DTC with anaplastic foci (97.8%) and PDTC (96.7%) compared with ATC (60.5%). The overall recurrence rate after initial remission was 30.8% in ATC, 25.9% in PDTC, and 6.7% in DTC with anaplastic foci. Pathologic diagnosis, preexisting goiter or tumors, along with tracheal and lymphatic/vascular invasion were correlated with recurrence (p < 0.001; p = 0.001, 0.006, 0.003, and 0.016, respectively). All patients without initial remission died due to local failure, and most patients with recurrence, apart from two PDTC patients, had distant metastasis. Overall mortality after initial curative-intent surgery was 58.1% in ATC, 8.7% in DTC with anaplastic foci, and 20% in PDTC.

CONCLUSIONS The initial remission of resectable tumors was higher and the recurrence rate was lower in DTC with anaplastic foci and PDTC compared with ATC. Careful monitoring of the development of distant metastasis is necessary, especially in patients with aggressive pathology with tracheal and lymphovascular invasion.