Clinical behavior of distant metastases of radioactive iodine-refractory differentiated thyroid cancer in children and adolescents

  • Background/Purpose: A few cases of  radioiodine-refractory distant metastases in pediatric differentiated thyroid cancer (pedDTC) have been published in the world. 

    Materials and methods: Papillary radioiodine-refractory pedDTC was diagnosed in 5 patients between 2014 and 2018. Male to female ratio is 4:1. TNM(8thed): T3N1bM1(pulm)-3, T4N1bM1(pulm)-1, T2N1aM1(pulm)-1. Total thyroidectomy with central dissections was performed in all the patients with additional unilateral neck dissection in 2 cases and bilateral in 2. The number of radioiodine therapies (RIT) ranged from 2 to 7. Single I-131 activities varied 1.1 – 7.4 GBq. ?umulative activities ranged 4.8 – 42.7GBq (median 17.9 GBq).

    Results: The follow-up period was 15-48 months (median 30,5 ±15,3). In the post RIT follow-up, at mean 15,6 ±12,6 months, distant metastasis progression was not determined. High
    levels of TgAb (>4000 ng/l) were noticed in 2 cases: in one case with high Tg level (426 – 842 ng/l) and one case with low Tg level (0,1-0,8 ng/l). The mean Tg level decreased after 2 RIT to 476-310 ng/ml and then increased after the next RIT to 544 ng/ml. TgAb level decreased from 5143 IU/l to 191 IU/l in one case and increased from 1800 IU/l to 4000 IU/l in the other.

    Conclusions: Radioactive iodine-refractory pedDTC can be observed in ages 4-17 years, most common in males (?ale:Female-4:1). Further long-term follow-up studies are necessary to update our knowledge of risk factors for recurrence, and late effects of treatment.  Multikinase inhibitors are the only treatment of choice in radioiodine-refractory pedDTC, but clinical experience is almost absent.


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