Radioactive iodine ablation (RAI)

The ATA Task Force recommends the use of 131I for the treatment of iodine-avid, persistent locoregional, or nodal disease that cannot be resected, and for known or presumed iodine-avid distant metastases. For patients with persistent disease after administration of 131I, the decision to pursue additional 131I therapy should be individualized based on clinical data and previous response. For patients without lymph node or distant metastases, there is no evidence that 131I can improve survival or reduce recurrence rates.[6]

To facilitate 131I uptake by residual iodine-avid disease, the TSH level should be above 30 mIU/L. This level can be achieved by withdrawing levothyroxine for at least 14 days. A low-iodine diet should also be followed for 2 weeks before therapy. RAI should be deferred for 2 to 3 months after exposure to iodinated CT contrast, and urine iodine excretion should be confirmed to be less than 75 µ/L. In patients who cannot mount an adequate TSH response or cannot tolerate profound hypothyroidism, recombinant human TSH may be used.

Therapeutic 131I administration is commonly based on either empiric dosing or whole-body dosimetry. Based on the lack of data comparing empiric treatment and treatment informed by dosimetry, the ATA Task Force was unable to recommend one specific approach. However, because of the differences in body size and iodine clearance in children compared with adults, all activities of 131I should be calculated by experts with experience in dosing children.

A posttreatment whole-body scan is recommended for all children 4 to 7 days after 131I therapy. The addition of single-photon emission CT with integrated conventional CT (SPECT/CT) may help to distinguish the anatomic location of focal uptake.While rare, late effects of 131I treatment include salivary gland dysfunction, bone marrow suppression, pulmonary fibrosis, and second malignancies.[44]

Because response to 131I may be observed up to 15 to 18 months after therapy, long intervals of at least 12 months are suggested before re-treatment.[6]

In a multicenter study of children and adolescents with differentiated thyroid carcinoma, 285 consecutive patients were treated with total thyroidectomy and RAI according to the ATA guidelines.[45]

In a multicenter study of children and adolescents with differentiated thyroid carcinoma, 285 consecutive patients were treated with total thyroidectomy and RAI according to the ATA guidelines.[45]

87% of the patients had no evidence of active disease at a median follow-up of 133 months.

In a single-center study of ATA pediatric low-risk differentiated thyroid cancer diagnosed between 2010 and 2020, 95 patients underwent total thyroidectomy followed by 131I therapy in 53% of patients.[46]

In a single-center study of ATA pediatric low-risk differentiated thyroid cancer diagnosed between 2010 and 2020, 95 patients underwent total thyroidectomy followed by 131I therapy in 53% of patients.[46]

There was no statistical difference in remission rates between patients treated with or without 131I therapy at 1 year (70% vs. 68.9%, respectively; P = .089) or last clinical evaluation (82% vs. 75.6%; P = .534).

In a single-center study of ATA pediatric low-risk differentiated thyroid cancer diagnosed between 2010 and 2020, 95 patients underwent total thyroidectomy followed by 131I therapy in 53% of patients.[46]

Over the study period, use of 131I in the patient population declined steadily, as the 2015 ATA Pediatric Differentiated Thyroid Cancer Guidelines recommended withholding 131I therapy in patients with low-risk disease. Accordingly, patients who received 131I therapy had longer follow-up (median, 5.8 years) than those who did not receive 131I therapy (median, 3.6 years).