[Utility of positron emission tomography with fluorodeoxyglucose (FDG-PET) in the evaluation of thyroid cancer: a systematic review].

After the initial thyroid cancer treatment, the detection of likely recurrences and/or metastases is made through the measurement of serum markers determinations and diagnostic image procedures. These techniques may be negative in spite of biochemical evidence of metastatic disease. The positron emission tomography with fluorodeoxyglucose (FDG-PET) has been proposed as an accurate method to detect it. The aim of this study is to present a synthesis of the evidences obtained from a systematic review regarding FDG-PET accuracy in locating suspected metastases of previously treated thyroid cancer, when the conventional methods failed to do it. A bibliographic review of all studies related to FDG-PET and differentiated thyroid cancer was made on MEDLINE, indexed until September 2005. Two hundred and sixteen citations were collected and 17 studies included, 71% were published after 2000. FDG-PET sensibility was high, with only one study presenting a sensibility lower than 75%. The specificity, examined in 12 studies was lower than 75% in 3 studies. There was at least one test compared to FDG-PET in 41% of the studies. The results point to FDG-PET as a useful diagnostic test to detect and localize thyroid cancer metastases, with direct implications in the treatment of these patients.