Endocrine Abstracts

JOINT2759

Background: Detecting cervical node metastasis prior to surgery in patients with differentiated thyroid cancer is essential for guiding the extent of thyroid surgery and neck dissection. Guidelines recommend performing thyroglobulin measurement in fine needle washout to improve the sensitivity of ultrasound (US)-guided fine needle cytology for the diagnosis of neck node metastasis. The choice of 1 ng/ml of thyroglobulin as cut-off value for diagnosing metastasis remains controversial. Confirmation of the metastatic disease by node dissection is not feasible in many cases, thus leading to a risk of misclassifying the patients’ status. In those cases, US node features are used to evidence patients’ status at later stage. However, cervical lymph node metastases usually remain stable for years after thyroidectomy, and US node features suggestive of malignancy often lack sensitivity.

Objective: To assess sensitivity of thyroglobulin measurement in fine needle washout for the diagnosis of thyroid cancer node metastasis.

Methods: For this retrospective monocentric study, data on eligible patients attending our onco-endocrinology from 2011 to 2024 were collected using electronic records. Inclusion criteria were: completion of presurgical fine needle puncture of suspicious lymph nodes; subsequent thyroglobulin measurement in the needle washout; subsequent thyroidectomy; eligibility for 131I therapy after thyroidectomy. Diagnostic accuracy was assessed using a composite reference standard: histopathological lymph node examination if the node was dissected, or presence of 131I uptake on postablation scintigraphy if the node was not.

Results: A total of 537 patients were screened for eligibility. For 63 patients, metastatic status of punctured lymph node was confirmed by neck node dissection report or by 131I scintigraphy. For 14 patients, the punctured lymph node was free of metastasis. Area under the ROC curve (AUC) was 0.91 (95% confidence interval 0.85 - 0.98). Sensitivity of thyroglobulin measurement in needle washout was 87 % (95% confidence interval 76.9 - 93.4) for the threshold of 1 ng/ml.

Conclusions: Thyroglobulin measurement in fine needle washout efficiently detects neck node metastasis of differentiated thyroid cancer. We use 131I scintigraphy combined with histopathological records as a reference standard for assessing diagnostic accuracy. More studies estimating sensitivity of this diagnostic test are needed to help clinicians in the therapeutic choice. Local registration: DEC24-307