Difference of clinical and radiological characteristics according to radioiodine avidity in pulmonary metastases of differentiated thyroid cancer

Abstract

Purpose: To evaluate differences in clinical, radiological and laboratory findings between pulmonary metastasis with and without radioiodine avidity in thyroidectomized differentiated thyroid cancer (DTC) patients with pulmonary metastasis who underwent high-dose I-131 treatment.

Methods: A total of 105 DTC patients with pulmonary metastasis (age, 48.7 ± 16.8 years; women/men, 78/27) were included. Clinical characteristics, chest computed tomography (CT), F-18 fluorodeoxyglucose positron emission tomography (F-18 FDG PET)/CT and thyroid-stimulating hormone (TSH)-stimulated serum thyroglobulin (s-Tg) level were compared between patients with and without radioiodine uptake in metastatic lung lesions. The response to I-131 treatment was evaluated with follow-up study.

Results: Eighty-nine patients (84.8 %, whole-body scan positive [WBSP] group) showed radioiodine uptake at pulmonary metastasis on post I-131 treatment whole-body scan (WBS) and 16 patients (15.2 %, WBS negative [WBSN] group) did not show uptake at pulmonary lesions on the WBS. Ninety percent and 87 % of the WBSP group had visible metastatic lesions on CT and F-18 FDG PET/CT; however, all of the patients in the WBSN group showed lesions on CT and F-18 FDG PET/CT. In seven (6.7 %) of 105 patients, CT and F-18 FDG PET/CT could not detect pulmonary lesions, which were diagnosed by post I-131 treatment WBS. Complete disease remission was achieved in six (5.7 %) patients and all of them were in the WBSP group.

Conclusions: Metastatic lesion was not visualized on chest CT or F-18 FDG PET/CT in 6.7 % of DTC patients with pulmonary metastasis and the lesion was visualized only on post I-131 treatment WBS. Complete remission was achieved in 5.7 % of DTC patients with pulmonary metastasis and the cured metastases were non-visualizing or micronodular lesions on chest CT and demonstrated radioiodine avidity on post I-131 treatment WBS.

Keywords: Differentiated thyroid cancer; I-131 treatment; Pulmonary metastasis; Radioiodine avidity.

Fig. 1

Representative images of post I-131 treatment WBS negative pulmonary metastasis. A 49-year-old woman who underwent total thyroidectomy due to papillary type differentiated thyroid carcinoma (DTC). a Chest CT demonstrated multiple metastatic lesions (arrows) in both lung fields and TSH-stimulated s-Tg was 34.1 ng/ml. Pulmonary metastases of DTC was diagnosed based on chest CT and TSH-stimulated s-Tg level. b Post I-131 treatment WBS obtained after 200 mCi I-131 administration revealed no remarkable uptake on the WBS. The patient was enrolled into the WBSN group

Fig. 2

Representative images of post I-131 treatment WBS positive and F-18 FDG PET/CT positive pulmonary metastasis. A 50-year-old man who underwent total thyroidectomy due to papillary type differentiated thyroid carcinoma (DTC). a F-18 FDG PET/CT demonstrated multiple metastatic lesions with faint FDG uptake in both lung fields and TSH-stimulated s-Tg was 831.1 ng/ml. Pulmonary metastases of DTC was diagnosed based on F-18 FDG PET/CT and TSH-stimulated s-Tg level. b Post I-131 treatment WBS obtained after 200 mCi I-131 administration revealed intense multiple focal uptakes on the WBS. The patient was enrolled into the WBSP group

Fig. 3

Representative images of post I-131 treatment WBS positive and F-18 FDG PET/CT negative pulmonary metastasis. A 22-year-old woman who underwent total thyroidectomy due to papillary type differentiated thyroid carcinoma (DTC). a F-18 FDG PET/CT revealed no demonstrable lesions in both lung fields and TSH-stimulated s-Tg was 3,217 ng/ml. b Post I-131 treatment WBS obtained after 180 mCi I-131 administration revealed intense and diffuse pulmonary uptakes on the WBS. Pulmonary metastases of DTC was diagnosed only by the WBS and the patient was enrolled into the WBSP group