Postoperative surveillance of differentiated thyroid carcinoma: rationale, techniques, and controversies.

Although differentiated thyroid cancer (DTC) is typically an indolent disease with a high rate of cure, recurrence is common (15%-30% of patients), even in early-stage disease. These high rates of recurrence have resulted in the widespread adoption of intensive posttherapy surveillance algorithms. Currently used strategies rely primarily on serial serum thyroglobulin measurements combined with cervical ultrasonography (US): US is utilized to search for recurrences within the thyroid bed or anterior cervical lymph nodes and as a guidance system for directed fine-needle aspiration biopsy of suspicious lesions. Positron emission tomography (PET) and coregistered computed tomography/fluorine 18 fluorodeoxyglucose PET are used primarily in the setting of non-iodine-avid tumors. Intensive surveillance has improved the ability to detect small-volume tumor recurrence with a sensitivity that surpasses current understanding of the clinical implications of detecting clinically occult residual or recurrent disease. Knowledge of currently used treatment and surveillance strategies is crucial for understanding the appropriate use of imaging studies, the clinical implications of imaging findings, and the appropriate use of US-guided tissue sampling in patients with DTC. Recent advances in the understanding of DTC tumor biology hold promise for improving the ability to predict tumor behavior and aggressiveness, thereby allowing more appropriate risk stratification, imaging surveillance, and treatment. (c) RSNA, 2008.