Objectives The correlation between a I-131 whole-body scan (WBS), a Tc-99m sestamibi (Tc-99m-MIBI) WBS, a computed tomography (CT) scan and the value of routine follow-up for I-131 WBS and thyroglobulin (Tg) levels in patients with lung metastases from differentiated thyroid cancer was assessed. Method Pulmonary metastases were detected in 32 patients out of 583 with differentiated thyroid cancer (DTC) who were admitted to our clinic between 1985 and 2004 (age range, 22-79 years; mean, 58 +/- 19 years; 15 women and 17 men). Pulmonary metastases were diagnosed by considering the I-131 WBS, increased Tg levels and/or other positive radiological findings. Papillary carcinoma was diagnosed in 15/32 patients and follicular carcinoma in 13/32. A mixed type found in 4/32 patients was classified histopathologically. A total of 3.7-53.65 GBq (100-1450 mCi) I-131 was given to each patient. The duration of follow-up ranged from 36 to 240 months. A I-131 WBS, the determination of Tg levels and/or a CT scan were carried out in the assessment of a diagnosis and follow-up of patients with lung metastases. A Tc-99m-MIBI WBS was performed on 19 patients who were chosen at random from the 583. Results Nineteen of 32 patients had lung metastases before they received the first I-131 treatment. Six of the 32 had distant-organ metastases other than in the lungs. Four of these six patients had only lung and bone metastases. Pulmonary metastases were observed on the I-131 WBS patients 31/32 (96.8%) whereas no pulmonary metastases, were detected on the CT scans in 3/32 patients. The last diagnostic whole-body scan (DWBS) was normal in 13/32 patients. At the first examination, the Tg levels in 27/32 (84.4%) patients were below 30 ng (.) ml(-1). At the final examination, 20/32 (62.5%) patients had Tg levels higher than 30 ng (.) ml(-1), while Tg levels were lower than 30 ng (.) ml(-1) in 12/32 patients. Tg levels decreased in 21/32 and increased in 3/32 patients. The I-131 WBS continued to be abnormal in 2/3 patients with increased Tg levels but became normal in one patient whose CT scan still showed macro-nodular lesions. Tg levels did not change significantly in 8/32 patients. The I-131 WBS became normal in 5/8 patients, while the CT scans for 4/5 showed micro-nodules. Metastases were detected in 12/19 patients who underwent Tc-99m-MIBI whole-body scanning: 18/19 showed metastases on the I-131 WBSs and 17/19 on the CT scans. Of the seven patients without a sign of metastasis on the Tc-99m-MIBI WBS, one was negative in terms of metastasis on the I-131 WBS and one on the CT scan. Fibrosis was observed on the CT scans of 2/32 patients. One patient developed dedifferentiation, as determined by the negative I-131 WBS and positive CT scan. Conclusion I-131 whole-body scanning and the determination of Tg levels are the most important procedures for the evaluation of lung metastases in differentiated thyroid cancer. Computed tomography is a useful addition to I-131 whole-body scanning. MIBI imaging alone may not be enough to detect lung metastases from differentiated thyroid cancer.
