Poorly Differentiated Thyroid Carcinoma: Single Institution Series of Outcomes.

ABSTRACT

BACKGROUND AND AIM: Poorly differentiated thyroid cancer (PDTC) is a rare but aggressive subtype of thyroid cancer that portends a poor prognosis. There remains a paucity of literature on PDTC outcomes. The aim of our study was to evaluate outcomes of PDTC in our tertiary care facility. PATIENTS AND METHODS: We identified all histologically confirmed PDTC cases from 1997-2018 treated at our Institution and collected data points in an IRB-approved registry. We then conducted a retrospective study to assess outcomes and identified factors associated with inferior outcomes. RESULTS: Twenty-three patients were identified with a median age at diagnosis of 60 years (range=39-89 years). Nineteen (83%) underwent total thyroidectomy. Eight (42%) patients had lymph node dissections and 2 (11%) underwent adjuvant radiation. Thirteen (68%) patients were treated with radioactive iodine (RAI). Those who underwent total thyroidectomy had a median overall survival (mOS) of 88 months, 5 year-OS of 56%, 5 year-local recurrence-free survival (LRFS) of 45%, and 5 year-distant recurrence-free survival (DRFS) of 36%. T4 disease had worse mOS (14 vs. 87 m, p=0.0082), and 5 year-LRFS rate (12 vs. 74%, p=0.0312) compared to T1-3. N0 disease had an improved mOS (172 vs. 32 m, p=0.0013), 5 year-LRFS rate (63 vs. 17%, p=0.0033), and 5 year-DRFS (57 vs. 0%, p=0.0252). Eight out of 23 patients (35%) were alive at last follow-up, with a median of 68 months (range=20-214). The most common cause of death was distant recurrence (73%). Six patients received systemic therapy with various tyrosine kinase inhibitors with a median duration on treatment of 7 months (range=1-30 months). CONCLUSION: Advanced T and N stage were factors associated with significantly inferior outcomes. While select patients benefited with systemic treatment, it remains unclear if intensified locoregional therapy should be considered in patients with PDTC.