Follow-up Protocol for Differentiated Thyroid Cancer Post-Thyroidectomy and RAI

Initial Follow-up Assessment

The American College of Radiology and the Annals of Oncology recommend that the first comprehensive assessment should be performed 6-18 months after initial treatment to evaluate response to therapy, including serum thyroglobulin (Tg) measurement, serum Tg antibodies (TgAb) measurement, and neck ultrasound (US) 1, 2, 3, 4
For patients who underwent total thyroidectomy and RAI ablation, a basal serum Tg level <0.2 ng/mL on thyroid hormone therapy or <1 ng/mL after TSH stimulation indicates excellent response to therapy, as recommended by the American College of Radiology and the Annals of Oncology 1, 5

The Annals of Oncology recommend that low-risk patients with excellent response should have serum Tg and TgAb measured every 12-24 months, and TSH maintained at 0.5-2 μIU/mL 1, 4, 6
The American College of Radiology recommends that intermediate-risk patients with excellent response should have serum Tg and TgAb measured every 12-24 months, and TSH maintained at 0.5-2 μIU/mL 1, 6
The Annals of Oncology recommend that high-risk patients with excellent response should have serum Tg and TgAb measured every 6-12 months, and TSH maintained at 0.1-0.5 μIU/mL 1
The Annals of Oncology recommend that patients with biochemical incomplete response should have serum Tg and TgAb measured every 3-6 months, and TSH maintained <0.1 μIU/mL 1, 6

The Annals of Oncology recommend that concomitant assessment of TgAb is mandatory with every Tg measurement, as these antibodies can interfere with Tg assays causing false-negative or false-positive results 1, 6
The Annals of Oncology recommend that Tg levels should ideally be measured with the same assay throughout follow-up to minimize variability 1
The Annals of Oncology recommend that short Tg doubling time (<1 year) is associated with poor outcomes and should prompt more comprehensive imaging evaluation 6

The American College of Radiology recommends that neck US is the first-line imaging investigation for DTC after initial therapy 2, 5
The American College of Radiology recommends that whole-body scintigraphy (WBS) is not utilized in low-risk patients without suspicion for recurrence and normal thyroid US 2, 5
The American College of Radiology recommends that FDG-PET/CT scanning is not recommended for routine surveillance if there is no evidence of residual disease 2, 5
The Annals of Oncology recommend that additional cross-sectional imaging should be considered if Tg or TgAb levels are rising 1, 6

In differentiated thyroid cancer (DTC) patients post-treatment, low Tg levels are expected and desired, indicating successful removal of all thyroid tissue, according to the National Comprehensive Cancer Network 7
Low thyroglobulin in patients with intact thyroid glands may indicate thyroglobulin synthesis disorders, as suggested by the American College of Radiology 8

In DTC follow-up, low Tg with negative TgAb indicates excellent response to therapy, as indicated by the American College of Radiology 8