Introduction: Retropharyngeal lymph node metastases (RPM) from differentiated thyroid carcinoma (DTC) are rare. Treatment includes surgical resection, radioactive iodine (RAI) therapy or external beam radiotherapy (EBRT). This study aims to define the considerations in treatment and prognosis for RPM in DTC.
Methods: Patients with a RPM and DTC were identified from an institutional database from 1999 to 2018. Patients with anaplastic or medullary DTC were excluded from the study. Clinical and tumor characteristics were recorded and patients were categorized into observation, non-surgical treatment or surgical resection. Disease specific survival (DSS), local RPM control, locoregional recurrence free probability (LRRFP) and distant recurrence free probability (DRFP) were calculated using the Kaplan-Meier method.
Results: Sixty-five patients were identified. The median follow-up from initial surgery was 78 months. Thirty-eight patients (58.5%) were female and the median age at initial presentation was 42 years. Initial histology was papillary carcinoma in 55 patients (84.6%), poorly differentiated in 7 (10.8%) and Hurthle cell carcinoma in 3 (4.6%). The majority had N1a or N1b disease at presentation (86.2%). The RPM was ipsilateral to the primary DTC in 52 patients (80.0%). In 53 patients (81.5%) RPM was a manifestation of recurrent disease.
Of the 65 patients, 27 (41.5%) were selected for surgical resection, 24 (36.9%) were observed and 14 (21.5%) had non-surgical treatment (RAI, EBRT and/or systemic therapy) following the diagnosis of a RPM.
In the surgical cohort, the median RPM size was 2.4cm (range 0.8 – 4.4cm). Size was found to be predictive of surgical resection versus observation (p < 0.001). Surgical approach was selected depending on the location of the RPM and presence of concurrent locoregional disease. A transcervical approach was performed in 19 patients (70.4%) and a transoral approach in 8 (29.6%). A transoral approach was reserved for patients with a superomedially located RPM. Following surgery, seven patients (25.9%) reported dysphagia and one patient (3.7%) developed a hypoglossal nerve injury.
Eight surgical patients (29.6%) had RPM resection at the time of initial surgery; none developed subsequent locoregional recurrence. Conversely, those that presented as recurrent disease were associated with multiple locoregional recurrences. Overall, the estimated local RPM control in patients treated with surgery was 92.1% at 3 years. At final follow-up, 13 patients (48.1%) had no evidence of structural disease.
In the entire cohort, the five-year LRRFP was 33.3% and five-year DRFP was 81.9%. Five-year DSS from RPM diagnosis was 88.7%. This suggests the presence of RPM is a surrogate marker for poor outcome for DTC patients.
Conclusions: Select patients with RPM from DTC are suitable for surgical resection. However, despite good local RPM control, the presence of a RPM appears to be a predictor of aggressive disease and a risk factor for distant metastasis.
