Outcomes of I-131 radioiodine treatment in differentiated thyroid cancer of pediatric and adolescent patients

Abstract

Background: The management of differentiated thyroid cancer in children and adolescents aims to reduce mortality rates and minimize treatment-related complications. However, there have been no reports in Thailand detailing clear clinical outcomes or complications occurring in either the acute or long-term phases in this patient group. Objective: To evaluate clinical outcomes and treatment-related complications following I-131 therapy in children and adolescent patients with differentiated thyroid cancer receiving treatment at the Nuclear Medicine Department, Siriraj Hospital. Methods: This retrospective study reviewed medical records of patients with differentiated thyroid cancer aged 21 years or younger at initial diagnosis who received I-131 treatment between January 2000 and December 2013. All patients were followed up for at least 1 year. Results: Among 78 patients, 33 (42.3%) achieved remission, while 45 (57.7%) were classified as non-remission. Within the non-remission group, 40 patients (51.3%) had persistent disease, 3 (3.8 %) showed progression and 2 (2.6%) experienced recurrence. In multivariate analysis, cervical lymph node metastasis only [OR= 6.17, 95% CI (1.17-32.62) p = 0.032] and cervical lymph node metastasis with distant metastases [OR= 20.47, 95% CI (2.31-181.15) p = 0.007] were both significantly associated with non-remission. Acute complications after I-131 treatment were observed in 28 patients, including gastritis (19.2%), thyroiditis (14.1%), and sialadenitis (12.8%). Late complications occurred in 10 patients, including atrophic changes of salivary glands (10.2%), salivary dysfunction (1.3%), and secondary primary malignancy (1.3%). The secondary primary malignancy was identified as mucoepidermoid carcinoma of right parotid gland in one patient Conclusions: Most pediatric and adolescent patients with differentiated thyroid cancer treated with I-131 did not achieve remission, with persistent disease being the most common outcome. Cervical lymph node metastasis, with or without distant metastasis, was significantly associated with non-remission. Treatment-related complications were generally low, with acute complications occurring more frequently than late complications. Second primary malignancy after I-131 therapy was rare in this cohort.