Paediatric Oncology
Figure 1: Fifteen-year-old Girl Diagnosed with T2mN1bM0 Papillary Thyroid Carcinoma
AB Thyroid bed Lymph node bed Lung metastases
Radioiodine Treatment Is Effective in Children with Disseminated Differentiated Thyroid Cancer The prevalence of distant metastases is high in children, with an incidence of 20–30%.25–27
total-body scan enables the detection of lung metastases.20–24 These
lung ‘micrometastases’ are not visible on chest X-ray or computed tomography; they are only evident on a 131I scan performed after total thyroidectomy and thyroid ablation. Unless detected in a 131I scan, such metastases remain silent for years. However, sooner or later they will emerge with a greater tumour burden.
Dissemination outside the lungs is very
rare. Unlike adult lesions, paediatric pulmonary DTC metastases are overwhelmingly miliary, seldom nodular and almost always functional.9,24,28,29
Among 95 Byelorussian children with radiation-induced DTC with lung metastases, 92 (96.8%) had miliary, disseminated-type pulmonary radioiodine uptake and only three (3.15%) had nodular uptake.24
This type of lung metastasis – miliary with disseminated lung radioidine uptake – was also typical in other studies.22,30
The high prevalence of functional metastases in pediatric DTC results in very effective radioiodine treatment. In publications to date, this modality achieved complete remission in the majority of children with lung metastases (see Figure 1).7,30 response rarely subsequently progressed31
Even patients with partial and over a 20-year
follow-up, only a few cause-specific deaths in pediatric patients with lung metastases were observed.9
After near-total thyroidectomy and modified lymnphadenectomy, 131I treatment was administered. In post-therapy total body scan (A), 131I uptake was visible in lung metastases, thyroid and the lymph node bed. Clinical staging was changed to M1. Lung computed tomography was negative. After four cycles of 131I therapy (cumulative activity 14.5GBq), complete scyntigraphic and biochemical remission was achieved (B).
post-operatively (p=0.001). Ten-year locoregional failure-free survival in children without distant metastases at diagnosis was 86.5% compared with 71.9% for those not treated with radioiodine (p=0.04).
It was recently demonstrated that although pre-pubertal children often suffer from advanced disease (e.g. extrathyroid extension, lymph node and distant metastases) compared with pubertal adolescents, disease outcome is similar in both groups if adequate treatment consisting of thyroid surgery and radioiodine is applied.17 These results are in agreement with a meta-analysis of remnant ablation outcomes in DTC patients of all ages, which determined that radioiodine reduced the risk of locoregional and distant recurrence.18
Nevertheless, it should be stressed that not all authors agree on the beneficial role of radioiodine in the post-surgical management of childhood DTC as there are studies in which radioiodine did not affect the outcome in children with DTC.13,19
In a recent large retrospective
study of 215 DTC patients
did not find any difference in incidence of recurrence in children regardless of whether they had been treated with adjuvant radioiodine treatment after total or near-total thyroidectomy.
Adjuvant Radioiodine Treatment Increases the Accuracy of Disease Staging
Another issue is that a substantial number of paediatric patients can only be properly staged on the basis of a radioiodine scan, preferably after high radioiodine activity. In about 20–50% of paediatric DTC patients affected with distant metastases, only a post-ablation
66
Use of Recombinant Human Thyrotropin- stimulating Hormone in Radioiodine Treatment of Childhood Differentiated Thyroid Cancer To maximise radioiodine uptake, serum TSH should be above 30mIU/ml. The only approved method by which to stimulate TSH in children is endogenous TSH stimulation after L-thyroxin (L-T4) withdrawal. L-T4 is usually withdrawn for four to five weeks, often with a mixed regimen including triiodothyronine for the first two to three weeks. It has been demonstrated that in children a shorter two-week withdrawal time may be sufficient for adequate endogenous TSH stimulation.32
Whichever protocol is applied, it often
leads to symptomatic hypothyroidism – a very unfavourable condition in a young individual who is still developing.
In cases of non-compliance with the preparation regimen or if there is a substantial thyroid remnant still producing thyroid hormones, TSH can be insufficiently stimulated. The use of rhTSH avoids many of these drawbacks; however, its use in children is not approved in Europe or the US and it can only be used ‘off-label’.
Ten children were evaluated for the success rate of thyroid remnant ablation with rhTSH-aided radioiodine treatment. In five cases treatment resulted in complete loss of radioiodine uptake and low thyroglobulin levels. In two patients there was some persistent, minimal (
There are limited data on the use of rhTSH for radioiodine treatment in this age group.33–35
in a EUROPEAN ONCOLOGY
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