18F-fluorodeoxyglucose positron emission tomography-computed tomography for suspected recurrent papillary thyroid...

To report the initial experience with combined 18F-fluorodeoxyglucose positron emission tomography (FDG PET)/computed tomography (CT) imaging for suspected recurrent papillary differentiated thyroid cancer (DTC) at Sunnybrook Health Sciences Centre (SHSC), Toronto.

Single institution retrospective study.

Consecutive patients from SHSC who underwent FDG PET/CT imaging for suspected recurrent DTC over a period of 2.5 years were identified and their charts reviewed.

Qualitative appraisal of FDG PET/CT imaging in suspected recurrent DTC.

Sixteen patients (14F, 2M) were identified accounting for 17 FDG PET/CT scans. Three scans (18%) in 3 different patients were reported as suspicious for recurrent disease in the neck (1-3 lesions) and were considered "positive". All were subsequently confirmed pathologically (4-13 positive lymph nodes post operatively). Prior conventional imaging was abnormal in two patients. Two patients had an elevated non-stimulated thyroglobulin (TG) < 10 ng/mL (4.9 and 9.4). The remaining patient had a TG < 0.3 ng/mL but was anti-TG antibody positive (84 IUx10-3/L). With a median follow up of 15 months (range 7-36) there were no false positive or negative scans. Incidental pathology (breast cancer, large bowel polyps) was identified on a further 2/17 scans (12%).

FDG PET/CT imaging is able to detect recurrent DTC in patients with low TG levels. It can complement conventional imaging findings and exclude distant FDG-avid metastases prior to surgery. It may underestimate the number of positive lymph nodes in the neck. Occult pathology may be identified with whole body FDG PET/CT.