Prognostic Indicators and Comparative Treatment Outcomes in High-Risk Thyroid Cancer with Laryngotracheal Invasion

Background: Laryngotracheal invasion occurs in a subset of patients with well-differentiated thyroid cancer (WDTC) and is associated with a poor prognosis. We aimed to analyze patterns and predictors/outcomes related to this high-risk manifestation.

Methods: This population-based analysis utilized the Surveillance, Epidemiology, and End Results (SEER) registry (2000 to 2015) to identify WDTC patients. Temporal trends and geographic variation in invasion rates were assessed. Logistic regression and propensity score matching were employed to identify predictors of secondary malignancy, mortality, and treatment impact on overall and thyroid cancer (TC)-specific survival.

Results: Of 131,721 WDTC patients, 1,662 (1.3%) had tracheal invasion and 976 (0.7%) had laryngeal invasion at diagnosis. Tracheal and laryngeal invasion rates declined from 3.7%-0.7% and 1.5%-0.6%, respectively, from 2000 to 2015. Compared to 98,835 noninvasive cases, patients with laryngotracheal invasion were older and more often male, Asian, and Hispanic (all P<0.001). This group had larger tumors with higher rates of nodal (N1: 61.8% vs. 15.1%) and distant metastases (M1: 9.3% vs. 0.4%). Age ≥55 years (hazard ratio [HR], 1.19; P=0.004) and metastases (HR, 1.75; P<0.001) increased TC-specific mortality, whereas the converse pattern was found for Asian race (HR, 0.63; P=0.002) and surgery (HR, 0.35; P<0.001). In rigorously matched groups to control confounding, adding radioactive iodine to surgery reduced mortality by 30% (P<0.001). However, external beam radiation and systemic therapy did not improve survival over surgery alone.

Conclusion: Laryngotracheal invasion is present in 0.7% to 1.3% of cases, conferring over double the mortality risk. Radioactive iodine with surgery improves outcomes in this aggressive WDTC subset.