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Thyroid Cancer
Case Study #10
Study Background:
A 50 year old male with a history of thyroid carcinoma treated with total thyroidectomy was imaged to elucidate the site of suspected recurrence due to rising serum thyroglobulin levels. CT imaging of the neck and chest revealed a small piece of soft tissue along the left side of the thyroid bed inferiorly against the trachea, which was non-specific for recurrence.
PET Imaging:
Fifty minutes after the injection of 677 MBq of 18F-FDG, images of the head, neck, chest, abdomen, and pelvis were obtained with a GE Advance tomograph (7 minutes emission, 3 minutes transmission data per bed position). Data were reconstructed using an OSEM algorithm and segmented attenuation correction. The PET study demonstrates an intense area of increased uptake in the area of the left thyroid bed near the trachea (blue arrow) which corresponds to the superior portion of the soft tissue abnormality seen on CT. The two foci of activity seen in the abdomen (long red arrows) are urine in the ureters. No other areas of abnormal FDG uptake are seen.
Discussion:
FDG-PET is a useful tool in the restaging of thyroidectomized patients with well-differentiated thyroid carcinoma and elevated serum thyroglobulin levels. Both sensitive and accurate, PET detected metastatic disease in 95% of all cases in one prospective study, and had positive and negative predictive values of 92% and 93%, respectively, in another. PET should be considered as a first-line diagnostic test in patients who have negative findings on conventional I-131 whole body scans and elevated serum thyroglobulin levels.
Reference:
Conti PS, Durski JM, Bacqai F, et al. Imaging of locally recurrent and metastatic thyroid cancer with positron emission tomography. Thyroid Aug 1999, 9:797-804
Chung JK, So Y, Lee JS, et al. Value of FDG PET in papillary thyroid carcinoma with negative 131I whole-body scan. J Nucl Med Jun 1999, 40:986-92
Wang W, Macapinlac H, Larson SM, et al. [18F]-2-fluoro-2-deoxy-D-glucose positron emission tomography localizes residual thyroid cancer in patients with negative diagnostic (131)I whole body scans and elevated serum thyroglobulin levels.
J Clin Endocrinol Metab Jul 1999, 84:2291-302
Helal BO, Merlet P, Toubert ME, et al. Clinical impact of (18)F-FDG PET in thyroid carcinoma patients with elevated thyroglobulin levels and negative (131)I scanning results after therapy. J Nucl Med Oct 2001, 42:1464-9
Frilling A, Tecklenborg K, Gorges R, et al. Preoperative diagnostic value of [(18)F] fluorodeoxyglucose positron emission tomography in patients with radioiodine-negative recurrent well-differentiated thyroid carcinoma.
Ann Surg Dec 2001, 234:804-11
Adler L and Bloom AD. Positron emission tomography of thyroid masses. Thyroid 1993, 3:195-200.
Images courtesy of:
Meridia Hillcrest Hospital
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