Post-Thyroidectomy Ultrasonography versus Thyroglobulin as a Surveillance Tool for Locoregional Recurrence in Patients with Differentiated Thyroid Carcinoma: A Single Centre 10-Year Study

Abhishek Mahajan^1*Vineeth Kurki²Pranjal Rai²NILESH P Sable²Ujjwal Agarwal²Richa Vaish²Nivedita Chakrabarty²SHREYA SHUKLA²Anil Keith Dcruz²Prathamesh Pai²Kumar Prabhash²Vanita Noronha²VIJAY PATIL²Nandini Menon²Sarbani Ghosh Laskar²Asawari Patil²Munita Bal²Swapnil Ulhas Rane²Neha Mittal²Pankaj Chaturvedi²

• ¹The Clatterbridge Cancer Centre, Liverpool, United Kingdom
• ²Tata Memorial Hospital, Mumbai, Maharashtra, India

Background: Differentiated thyroid cancer (DTC; including papillary and follicular thyroid cancers) has favourable survival outcomes, with related mortality below 10%. However, 20–30% of patients experience recurrence. Surveillance primarily relies on neck ultrasonography (US) and serum thyroglobulin (Tg) assessment. Purpose: This study evaluated the diagnostic performance of neck US in detecting locoregional recurrence following total thyroidectomy and compared its effectiveness with serum Tg. Materials and Methods: This retrospective, single-centre study analysed 941 DTC patients who underwent total thyroidectomy and neck US between 2009 and 2019. Suspicious US findings were correlated with serum Tg levels and anti-thyroglobulin antibody status. Disease persistence (<6 months) /recurrence (>6 months) was confirmed via fine-needle aspiration cytology/biopsy, iodine scintigraphy, CT, or PET-CT. Patients without US-detected lesions were assessed clinically, biochemically, and via follow-up US. Results: Neck US had a sensitivity of 98.9%, specificity of 63.1%, positive predictive value (PPV) of 50.7%, negative predictive value (NPV) of 99.3%, and an accuracy of 73.01%. Serum Tg (cutoff 1.8 ng/ml derived from receiver operating characteristic analysis) had a sensitivity of 69.2%, specificity of 91.8%, PPV of 61.4%, NPV of 94.1%, and an accuracy of 88.28%. Among 149 patients with US-detected lesions and Tg <1.8 ng/ml, 22 (14.8%) had locoregional recurrence. Five of 43 patients with Tg <0.1 ng/ml had confirmed recurrence. Among lymph nodes ≤6 mm in short-axis diameter with an indistinct fatty hilum, 69.6% were benign. Persistence was detected in 38.5% of patients within six months post-treatment, whereas most true recurrences (61.5%) manifested after six months. Conclusion: Neck US is highly sensitive but moderately specific for detecting locoregional recurrence post-thyroidectomy, complementing Tg. Study limitations include its retrospective design, single-centre setting, and lack of inter-observer variability assessment. A risk-adapted multimodal surveillance strategy with 6-monthly US for two years is recommended.