Iodine-131 treatment and high-resolution CT: results in patients with lung metastases from differentiated thyroid carcinoma

Abstract

Between 1984 and 2002, pulmonary metastases were detected in 42 (4%) out of 1,023 patients with differentiated thyroid carcinoma (DTC) in our department. The age at diagnosis ranged from 6 to 77 years. Lung metastases were diagnosed by both increased thyroglobulin (Tg) levels and positive uptake of iodine-131 on scans, and/or positive radiological findings. The primary tumours were histologically classified as papillary (30 patients), follicular (nine patients) and poorly differentiated (two tall cell, one insular carcinoma). The duration of follow-up ranged from 24 to 228 months. The end-results of the (131)I therapy were evaluated. The treatment of choice was (131)I therapy of metastases after total thyroidectomy plus lymph node dissection (if lymph node metastases were present). Applied single and total (131)I activities were 1.8-10.4 GBq and 5.5-43.7 GBq, respectively. Lung metastases were present at the time of diagnosis in 30 patients and developed during the follow-up period in the remaining 12. Twelve patients with extensive metastases died of thyroid carcinoma and another died due to secondary malignancy (malignant mesothelioma). Ten patients with lung metastases remain completely free of disease and are probably cured, while another seven were stable at the time of study. Three- and five-year survival rates were 86% (36/42) and 76% (32/42), respectively. To define the diagnostic value of high-resolution computed tomography (HRCT) and identify the distinctive features of lung metastases from DTC, 22 patients were further examined with HRCT within 2 weeks of the initial diagnosis of lung metastases and the results were compared with chest X-ray findings. HRCT detected metastases in 10 out of 14 patients with a normal chest X-ray and confirmed metastases in all patients with positive (n=5) and suspicious (n=3) chest X-ray. HRCT did not show any abnormalities in four patients with positive lung uptake on (131)I whole-body images. Stage of disease, existence of distance metastases other than to the lung, and HRCT characteristics were significant prognostic variables. Lung metastases from DTC can be cured with (131)I therapy in a considerable number of patients, especially when they are not associated with other distant metastases; they should therefore be treated at an early stage. HRCT clearly improved diagnostic ability in the evaluation of lung metastases compared with chest X-ray and should be the primary method when radiological correlation is needed. The main, and new, finding of the study is that HRCT not only improves diagnostic ability but is also of prognostic value.

Pulmonary metastases in differentiated thyroid cancer: efficacy of radioiodine therapy and prognostic factors

“…The size of pulmonary metastases was usually !1 cm, which was below the spatial resolution of chest X-ray. Chest CT could enhance the diagnostic accuracy in most patients with normal chest X-ray and had an additive effect to 131 I-WBS and Tg level (11). According to nodule size on chest CT, pulmonary metastases were divided into three categories: i) normal (nZ27); ii) micronodular (%1 cm, nZ212) and iii) macronodular (O1 cm, nZ17).…”

“…However, pulmonary metastases are more often encountered in patients with papillary carcinoma and their radiological size is usually !1 cm and frequently below the spatial resolution of the chest X-ray. Chest computed tomography (CT) is preferred over chest X-rays and it enhances the diagnostic accuracy in most patients with normal chest X-ray findings (11). Thus, it is useful for the detection of pulmonary metastases of DTC and is able to measure the node size of metastases accurately.…”

Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Taskforce

“…Pulmonary micrometastases should be treated with radioiodine therapy, repeated every 6-12 months as long as disease continues to respond, as the highest rates of complete remission are reported in these subgroups (243,248,255)-Recommendation A R59. The selection of radioiodine activity to administer for pulmonary micrometastases can be empiric (100-300 mCi) or estimated by dosimetry to limit whole body retention to 80 mCi at 48 hours and 200 cGy to the red bone marrowRecommendation C Macronodular pulmonary metastases may also be treated with radioiodine if demonstrated to be iodine avid.…”

Carcinoma diferenciado de tireóide: avaliação inicial e acompanhamento

“…Um estudo avaliou pacientes com metástases pulmonares diagnosticados tanto por incremento nos níveis de tireoglobulina, captação de 131 I no RCT ou achados radiológicos positivos (46). A fim de definir o valor diagnóstico da tomografia de alta resolução, 22 pacientes foram avaliados por este exame e os resultados comparados com o RX de tórax.…”