Poorly Differentiated Thyroid Carcinoma: Single Institution Series of Outcomes

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.

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.

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).

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.