Endocrine Abstracts

Introduction: Pediatric differentiated thyroid carcinoma (DTC) is a rare disease. In the literature, there are limited data for this type of tumor; in particular, it has never been evaluated the efficacy of radioiodine treatment with 131-I after 4-6 weeks from thyroid hormone withdrawal (THW) compared to the use of recombinant TSH (rhTSH); for this reason, the decision is often left to the experience of the team.

Aim: To compare the efficacy and safety of radioiodine treatment after THW or rhTSH.

Patients and Methods: We retrospectively evaluated 337 DTC patients, referred to our institution from 1966 to 2022. Inclusion criteria: age at the time of diagnosis <18 year; histologic confirmation of DTC; at least one radioiodine treatment with 131-I. Patients who underwent initial radioiodine treatments in hypothyroidism after THW and subsequent radioiodine treatments in euthyroidism after rhTSH stimulation, were excluded. We divided the patients according to the type of radioiodine treatment: Group A (123 patients treated after THW) and Group B (214 patients treated after rhTSH).

Results: Epidemiological, clinical, and pathological characteristics were similar in the two groups. Group A was submitted to a higher number of 131-I courses (2.3±1.8 sessions vs 1.6±1.4) and a higher 131-I cumulative activity than Group B (201.2±236.7 mCi vs 123.3±176.6). Despite the higher intensity of radioiodine treatment, due to a longer follow-up (37.0±12.7 years vs 9.8±7.2), no significant differences were observed in the last assessment (excellent response: 83.9% vs 74.8%; biochemical incomplete response 12.7% vs 20.5%; structural incomplete response 3.4% vs 4.7; P = 0.113) and adverse reactions between the two groups.

Conclusions: This study showed that rhTSH is equivalent to THW. For this reason, and considering the significant benefits, it would be desirable to extend the use of rhTSH in radioiodine therapy to all patients with DTC occurring in the pediatric age.