Abstract
BACKGROUND: Gross extrathyroidal extension (ETE) is one of the most important predictors of survival in papillary thyroid carcinoma (PTC). The aim of this study is to determine the impact of gross ETE to the recurrent laryngeal nerve alone (RLNT4aETE) on survival. METHODS: After institutional review board approval, adult PTC patients were identified from an institutional database undergoing initial surgery for well-differentiated thyroid carcinoma from 1986 to 2020. Patients were classified as having no gross ETE, gross ETE to strap muscles only (T3bETE), RLNT4aETE, or gross ETE involving other adjacent structures (otherT4aETE). Disease-specific survival (DSS) was calculated using the Kaplan-Meier method and groups were compared using the log-rank test. RESULTS: There were 8030 patients included in the analysis; 7578 patients (94.2%) with no gross ETE, 197 (2.4%) with T3bETE, 40 (0.5%) with RLNT4aETE, and 215 (2.7%) with otherT4aETE. The estimated 10-year DSS for patients with no gross ETE, T3bETE, RLNT4aETE, and otherT4aETE in the whole cohort were 99.2%, 95.7%, 96.9%, and 82.5% respectively (P < 0.0001). After controlling for age, nodal and distant disease stage, RLNT4aETE patients had a similar DSS to T3bETE patients, when compared to no gross ETE patients (HRs 2.91 versus 2.28 respectively). In the ≥55-year-old cohort, the 10-year DSS for patients with no gross ETE, T3bETE, RLNT4aETE, and otherT4aETE were 97.7%, 89.4%, 90.9% and 67.6% respectively. CONCLUSION: RLNT4aETE patients appear to have a similar DSS to T3bETE patients. This highlights the heterogeneity within the current T4a cohort and supports the downstaging of RLNT4aETE patients to the T3b classification.