Is Chest X-ray or High-Resolution Computed Tomography Scan of the Chest Sufficient Investigation to Detect Pulmonary Metastasis in Pediatric Differentiated Thyroid Cancer?

C.S. Bal; Ajay Kumar; Prem Chandra; S.N. Dwivedi; S. Mukhopadhyaya

Disclosures

Thyroid. 2004;14(3) 

In This Article

Abstract and Introduction

We reviewed the clinical characteristics, pattern of disease at presentation, histopathologic subtype, treatment, course, and outcome of differentiated thyroid cancer (DTT) in children and adolescents presenting with pulmonary metastasis and tried to assess the effectiveness of routine chest x-ray and high-resolution computed tomography (CT) scan of the chest vis-à-vis 131I whole-body scan (WBS) in revealing pulmonary metastasis. In our series of 1754 patients, 122 (7%) were 20 years of age or younger, of whom 28 (23%) had pulmonary metastasis. Mean age was 13.9 ± 4.4 years (F:M ratio = 12:16). All but 2 patients had undergone near-total thyroidectomy with some form of neck dissection. Histopathologic examination was papillary in 89% and follicular in 11% cases, with confirmed nodal metastasis in all. Twenty-one (75%) patients had normal chest x-ray. However, WBS revealed pulmonary metastasis in all cases. In 15 (54%) children pulmonary metastasis was detected by first postsurgery 2–3 mCi 131I WBS and in 4 (14%) patients by postablation 131I WBS. Seven cases (25%) and 2 cases were detected by first and second posttherapy 131I WBS, respectively. No statistically significant difference was observed in any of the demographic or clinical parameters in patients in whom pulmonary metastasis was detected by first postsurgical low-dose WBS versus those in whom metastasis was discovered at a later stage. When chest x-ray–positive children were compared to x-ray–negative children, a statistically significant difference was observed only for mean first dose, cumulative dose, and total number of doses of 131I, which were significantly higher in x-ray–positive children. Eighteen of 21 children who had normal chest x-ray also underwent CT scan of the chest. CT could detect micronodular pulmonary shadows in 5 (28%) children only. Complete radioiodine treatment and outcome information was available in 20 patients. Mean first dose and cumulative doses of administered 131I were 75.4 ± 39.5 mCi and 352 ± 263 mCi, respectively. After an average number of 3.3 doses of 131I and mean duration of 33.2 ± 28.5 months, pulmonary lesions disappeared in 14 (70%) patients and thyroglobulin (Tg) becoming undetectable. In 4 children, however, there was no radiologic or scintigraphical evidence of pulmonary metastasis, Tg was high and in 2 patients, disease was persisting clinically. To conclude, a large majority of pediatric patients with DTC have x-ray– and even high-resolution– negative pulmonary metastasis. However, these metastases are 131I avid, and thus are amenable to detection and treatment with radioiodine. Therefore, postsurgical evaluation with 131I is recommended in all children and adolescents.

Differentiated Thyroid Cancer (DTC) is a rare disease in the general population and uncommon in children and adolescents.[1–4] Among all the malignancies in the pediatric age group, the reported incidence of DTC is only 1%–2%.[5–9] DTC behaves more aggressively in the pediatric age group, with a high incidence of pulmonary metastasis at the time of initial diagnosis.[7,9–18] Chest x-ray is routinely used as the baseline investigation in these patients and occasionally high-resolution computed tomography (HRCT) is performed to establish the pulmonary metastasis. However, there has been no attempt in the to assess the ability and effectiveness of these investigative modalities vis-à-vis 131I whole-body scan (WBS) in revealing pulmonary metastasis from DTT, particularly in children. Furthermore, because DTC in children and adolescents has a favorable prognosis, many children do not undergo 131I treatment, thereby losing the opportunity of detecting pulmonary metastasis by WBS. There is the possibility that the undetected pulmonary metastasis may reduce disease-free survival, increase morbidity and mortality in the future, and is likely to be revealed in serial chest x-rays as pulmonary recurrence occurring late during long follow-up, while it had been present from the beginning. Therefore, there is a need for developing the best management strategy in pediatric patients with thyroid cancer for early detection of distant metastasis (mostly pulmonary) and their effective treatment in order to optimize their recurrence and survival profile. Unfortunately, there are few publications addressing this particular issue in detail.[16–18]

Therefore, we critically reviewed the clinical characteristics, pattern of disease at presentation, histopathologic subtype, treatment, course, and outcome of DTC in children and adolescents presenting with pulmonary metastasis and compared 131I WBS with chest x-ray and chest CT in the diagnosis/evaluation of pulmonary metastasis.

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