PET/CT Detection of Fludeoxyglucose F 18 Injection (18F FDG)1-avid, Radioiodine Negative Recurrent Thyroid Cancer

Samart Rajchadara, MD and Ananya Ruangma, PhD,
Data courtesy of Bangkok General Hospital, Bangkok, Thailand

A 38-year-old female presented with a left breast mass, which initially proved to be benign following an examination and aspiration biopsy. However, additional tests revealed papillary thyroid carcinoma coexisting with nodular goiter. In view of the diagnosis of papillary thyroid carcinoma, the patient underwent a near total thyroidectomy. A histopathology of the surgical specimen confirmed the diagnosis of encapsulated papillary microcarcinoma of the right lobe without capsular or vascular invasion. Due to high serum thyroglobulin (Tg), the patient was referred for high-dose radioiodine therapy for ablation of residual thyroid, where 100 mCi of 131I was administered. Six months post-131I large dose therapy, the patient underwent a follow-up Tg and 131I whole-body planar scan. Although the follow-up 131I whole-body scan was negative, the Tg was high, which suggested the possibility of radioiodine negative metastases or recurrence. Since radioiodine negative thyroid carcinoma recurrences are often poorly differentiated and Fludeoxyglucose F 18 injection (18F FDG)1-avid, the patient underwent a 18F FDG PET/CT scan.

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Fludeoxyglucose F 18 injection (18F FDG) is indicated for positron emission tomography (PET) imaging in the following settings:

Oncology: For assessment of abnormal glucose metabolism to assist in the evaluation of malignancy in patients with known or suspected abnormalities found by other testing modalities, or in patients with an existing diagnosis of cancer.

Cardiology: For the identification of left ventricular myocardium with residual glucose metabolism and reversible loss of systolic function in patients with coronary artery disease and left ventricular dysfunction, when used together with myocardial perfusion imaging.

Neurology: For the identification of regions of abnormal glucose metabolism associated with foci of epileptic seizures.

Radiation Risks: Radiation-emitting products, including fludeoxyglucose F 18 injection, may increase the risk for cancer, especially in pediatric patients. Use the smallest dose necessary for imaging and ensure safe handling to protect the patient and health care worker.

Blood Glucose Abnormalities: In the oncology and neurology setting, suboptimal imaging may occur in patients with inadequately regulated blood glucose levels. In these patients, consider medical therapy and laboratory testing to assure at least two days of normoglycemia prior to fludeoxyglucose F 18 injection administration.

Adverse Reactions: Hypersensitivity reactions with pruritus, edema and rash have been reported; have emergency resuscitation equipment and personnel immediately available.

Siemens' PETNET Solutions is a manufacturer of Fludeoxyglucose F 18 Injection (18F FDG). Indication and important safety information as approved by the US Food and Drug Administration can be found at the links below for 18F FDG, adult dose 5-10 mCi, administered by intravenous injection.

Full Prescribing Information Fludeoxyglucose F 18 Injection (5-10 mCi) as an intravenous injection in adults