Evaluation of I Accumulation in Neck Region of Patients with Thyroid Cancer Post Total Thyroidectomy

Received 4/8/2004; revised 5/20/2004; accepted 5/28/2004. For correspondence or reprints contact: Ya-Wen Chuang, M.D., Department of Nuclear Medicine, Kaohsiung Medical University Chung-Ho Memorial Hospital, 100 Tzyou 1st Road, Kaohsiung 807, Taiwan, ROC. Tel: (886) 7-3121101 ext. 7153, Fax: (886)7-3117521, E-mail: [email protected] Background: The aim of this retrospective study is to evaluate neck lesions detected on I scan post I treatment following recent surgical ablation of total thyroidectomy. Methods: These lesions were determined by using all available clinical, laboratory and radiological information. There were 51 patients with differentiated thyroid cancers (44 papillary and 9 follicular carcinoma with exception of medullary, anaplastic or poorly differentiated thyroid carcinoma) referred to our department between 1997 and 2002, ages from 14 to 67 years (mean age: 45 years old) and included into this study. Images were obtained 72 h after administration of an oral dose of 30 mCi (1,170 MBq) I-sodium iodide. All of them abstained from foods or drugs containing iodine at least 4 to 6 weeks. Results: Hot spots at thyroid beds or linear foci over midline of the neck region above thyroid area (106/109, 97.25%) are mainly residual thyroid tissue although complete surgical ablation is performed. Some I uptake may be seen outside the thyroid remnant (4/6, 66.67%), are mostly malignant particularly at the same side of tumor location. Tumor invasion to capsule, lymph nodes, or fasciae of muscles is confirmed on reports of pathology, producing heterogeneous or amorphous pattern. Conclusion: Hot spots or linear foci of neck region are frequently benign remnant, especially if they are focal and located at thyroid beds or midline of the neck region. In addition, our data indicate no strong relationship between surgical completeness of the thyroidectomy and significance of I accumulation in thyroid area. Any area of I uptake outside thyroid beds suggest statistically higher probability of recurrence in the future even the I dose administered has eradicated most of the residual thyroid cells.