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18F-FDG PET has demonstrated its usefulness in detecting recurrences of differentiated thyroid cancer (DTC) with high thyroglobulin (Tg) levels and negative 131I whole-body scan (WBS); however, the number of patients analyzed is low and different studies report disparate results.To estimate the diagnostic accuracy of 18F-FDG PET in this subgroup of patients.Fifty eight patients (64 18F-FDG PET studies) with histologically proven DTC treated with total thyroidectomy followed by at least one session of 131I therapy for the ablation of thyroid remnants were retrospectively analyzed. Results were verified by pathology, clinical follow-up, response to treatment, or by comparison with conventional diagnostic methods. Sensitivity (Se), specificity (Sp), likelihood ratios (LR), diagnostic accuracy (DA), positive and negative predictive values (PPV, NPV), and Tg levels were calculated for patients with positive and negative 18F-FDG PET results.Twenty seven studies were true positives, 1 false positive, 25 true negatives, and 11 false negatives. Se was 71 %, Sp 96 %, PPV 96.4 %; NPV 69.4 %, DA 81.3 %, positive LR 17.75, and negative LR 0.3. The mean Tg level was 202.34 ng/ml in patients with positive 18F-FDG PET and 40.94 ng/ml in those with negative 18F-FDG PET; the difference between the two groups (161.4 ng/ml) was significant at p0.05.18F-FDG PET is a useful for detecting residual or recurrent DTC in patients with elevated Tg and negative 131I WBS.

This study aimed to assess the results obtained with the positron emission tomography (PET) and conventional anatomic imaging methods (CT scan and MRI) in the diagnosis of suspicion of tumor recurrence in head and neck cancers.Thirty patients with suspicion of tumor recurrence due to head and neck cancers were reviewed retrospectively. Consequently, 34 PET studies were performed. The images were obtained in the PET Institute of Madrid. They were interpreted by visual and semiquantitative analysis. The results were confirmed with clinical follow-up, response to treatment or with histological studies in some cases.Sensitivity and specificity of the PET were 95.6% and 81.8% respectively, while it was 65% and 80% for the CT scan/MRI.We can conclude that PET provides better results than conventional imaging techniques in the detection of head and neck cancer recurrence.

This study aims to evaluate the impact of Positron Emission Tomography on therapeutic decisions in patients with suspicion of recurrence of head and neck cancers.The diagnostic and therapeutic impact of FDG-PET was evaluated in 59 of 60 studies performed in a sample of 54 patients. The impact was graded on five levels (high, moderate, low, no impact and negative impact) following the Hicks et al. classification modified by us.The FDG-PET impact was high in 28 studies (47.46 %), moderate in 7 (11.86 %), low in 20 (33.90 %), no impact in 3 (5.09 %) and finally negative impact in 1 study (1.69 %).FDG-PET is useful in the management of patients in 59.32 % of the studies with indeterminate physical examination and conventional imaging tests. This paper supplies new data since we did not find any studies showing statistical results on therapeutic impact of FDG-PET in head and neck cancers in a systematic review of the literature made by our group.