Serial Neck Ultrasound is More Likely to Identify False-Positive Abnormalities than Clinically Significant Disease in Low-Risk Papillary Thyroid Cancer Patients

Abstract

Objective American Thyroid Association (ATA) low-risk papillary thyroid cancer (PTC) patients without structural evidence of disease on initial posttreatment evaluation have a low risk of recurrence. Despite this, most patients undergo frequent surveillance neck ultrasound (US). The objective of the study was to evaluate the clinical utility of routine neck US in ATA low-risk PTC patients with no structural evidence of disease after their initial thyroid surgery. Methods We performed a retrospective review of 171 ATA low-risk PTC patients after total thyroidectomy, with or without radioactive iodine (RAI) ablation, who had a neck US without suspicious findings after therapy. The main outcome measure was a comparison of the frequency of finding false-positive US abnormalities and the frequency of identifying structural disease recurrence. Results Over a median follow-up of 8 years, 171 patients underwent a median of 5 neck US (range 2–17). Structural recurrence with low-volume disease (≤1 cm) was identified in 1.2% (2/171) of patients at a median of 2.8 years (range 1.6–4.1 years) after their initial diagnosis. Recurrence was associated with rising serum thyroglobulin (Tg) level in 1 of the 2 patients and was detected without signs of biochemical recurrence in the other patient. Conversely, false-positive US abnormalities were identified in 67% (114/171) of patients after therapy, leading to additional testing without identifying clinically significant disease. Conclusion In ATA low-risk patients without structural evidence of disease on initial surveillance evaluation, routine screening US is substantially more likely to identify false-positive results than clinically significant structural disease recurrence.

Papillary Thyroid Carcinoma Recurrence: Low Yield of Neck Ultrasound With an Undetectable Serum Thyroglobulin Level

“…The second was a case series of 5 patients with recurrence and undetectable serum Tg levels, but only 3 of the recurrences were in the neck, and none were identified by neck US . In the third study, surveillance neck US found recurrence in only 1 of 170 patients without biochemical signs of recurrence . Our results suggest that an undetectable serum Tg level measured by a highly sensitive assay predicts a very low rate of local recurrence and could be used to discriminate which patients should undergo neck US surveillance.…”

“…[15][16][17] There are few studies evaluating the rate of recurrence when the serum Tg is undetectable, with one recent study reporting that routine screening US identified recurrence in only 1 of 170 patients without signs of biochemical recurrence. 18 Moreover, the authors reported false-positive US abnormalities in 67% of patients (114 of 171) after therapy, leading to additional testing without identifying clinically significant disease.…”

Follow-up of low risk thyroid cancer patients: can we stop follow-up after 5 years of complete remission?

“…Repeating stimulated Tg testing in these patients at the fifth year of follow-up after primary treatment can help to reclassify these patients as in excellent response (in up to 98% of patients initially classified as indeterminate response and in 40% of the patients classified as a biochemical-incomplete response) (61).…”

Contemporary Debates in Adult Papillary Thyroid Cancer Management

“…These patients can be safely followed with periodic (every 12-24 months) serum thyroglobulin and thyroglobulin antibodies assays and neck palpation, without routine use of ultrasonography. Repeated neck ultrasound assessment in these patients may lead to more false positive findings (up to 67%) than true disease (<1.2%) (150,151). Undetectable thyroglobulin levels in patients with initially high-risk cancers may require additional, second-line diagnostic procedures to rule-out disease (see following section), as the absence of the circulating tumor marker may simply reflect the dedifferentiation of the residual neoplastic foci and their loss of ability to synthesize or secrete thyroglobulin.…”