Predictive factors for nodal recurrence in differentiated thyroid cancers.

Introduction: Differentiated thyroid carcinoma usually has a good prognosis. Primary treatment is surgery, followed by radioactive iodine ablation based on risk stratification. The incidence of local and distant recurrence is 30%. Recurrence can be managed surgically or with multiple cycles of radioactive iodine ablation. There are multiple risk factors for structural disease recurrence proposed by the American Thyroid Association. In this study, we attempted to study the risk factors of structural recurrence in differentiated carcinoma thyroid and the pattern of recurrence in patients with node negative thyroid cancer who underwent total thyroidectomy.

Methodology: This study selected a retrospective cohort of 1498 patients with differentiated thyroid cancer: out of these, 137 patients who presented after thyroidectomy with cervical nodal recurrence from January 2017 to December 2020 were included. The risk factors for central and lateral lymph node metastasis were analysed by univariate and multivariate analyses, including age, gender, T-stage, extrathyroidal extension, multifocality and high-risk variants. In addition, the presence of TERT/BRAF mutations was studied as a risk factor for central and lateral nodal recurrence.

Results: Out of 1498 patients, 137 who fit the inclusion criteria were analysed. Majority were female (73%); mean age was 43.1 years. Lateral compartment neck nodal recurrence was more common (84%), while isolated central compartment nodal recurrence occurred only in 16%. Most recurrences were seen in the first 1 year (23.3%) or after 10 years post-total thyroidectomy (35.7%). On univariate variate analysis, multifocality, extrathyroidal extension and high-risk variants stage were significant factors for nodal recurrence. However, on multivariate analysis for lateral compartment recurrence, multifocality, extrathyroidal extension and age were found to be significant. On multivariate analysis, multifocality, extrathyroidal extension and presence of high-risk variants were significant predictors of central compartment nodal metastasis. ROC curve analysis showed AUC for ETE (AUC-0.795), multifocality (AUC-0.860), presence of high-risk variants (AUC-0.727) and T-stage (AUC-0.771) as sensitive predictive factors for central compartment. 69 percent patients with very early recurrences (<6 month) had TERT/BRAF V600 E mutations.

Conclusion: In our study, we have noted extrathyroidal extension and multifocality as significant risk factors for nodal recurrence. BRAF and TERT mutations are associated with aggressive clinical course and early recurrences. There is limited role of prophylactic central compartment node dissection.