Ethanol Ablation of Metastatic Lymph Nodes in Patients with Papillary Thyroid Carcinoma - Predictors of Clinical Outcome.

Context: Ethanol Ablation (EA) is a treatment option in recurrent or persistent metastatic lymph nodes (MLN) from Papillary Thyroid Carcinoma.

Objective: To assess whether ultrasonographic characteristics of the MLN, history of lymph node surgery, aggressive histological subtype, or BRAF V600E mutation in the primary tumor predict long-term response from EA.

Methods: Seventy-five patients who received EA at a tertiary referral center were included. We evaluated treatment response from the most recent clinically indicated examination, or a study-specific examination. BRAF analysis and review of histological subtypes in the primary tumor were conducted.

Results: Median interval from initial surgery to follow-up was 119 months (range, 39-471). Pure cystic MLN had a better outcome than the solid and partially cystic MLN (13/13, 100% vs. 90/121, 74%, p=0.039). Small MLN (≤ 0.5 ml) had a higher response rate compared to larger lesions (71/92, 77% vs. 10/19, 53%, p=0.045). We observed no difference in EA-response between patients with or without the BRAF V600E mutation (80/99, 81% vs. 17/25, 68%, p=0.181) or an aggressive subtype (22/24, 92% vs. 75/100, 75%, p=0.099) in their primary tumors. EA achieved similar rates of locoregional disease control in neck regions with or without previous lymph node surgery (66% vs. 63%, p=0.825).

Conclusion: EA was highly effective in pure cystic MLN. Partially cystic or non-cystic MLN over 0.5 ml were less responsive, though many of these MLN still showed a lasting response. BRAF V600E mutation, aggressive histological subtype or absence of prior lymph node surgery, did not negatively impact EA response.