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Aims: To evaluate the efficacy and clinical impact of Positron Emission Tomography with FDG (FDG-PET) in patients with suspected recurrent head and neck cancer or distant metastases., Materials and Methods: Sixty patients (12 women and 48 men) with suspicion of recurrent head and neck cancer and ambiguous conventional imaging modalities. In all patients a whole body scan was performed with FDG-PET in fasting patients following i.v. administration of 370-444 MBq FDG. The results were confirmed by histology and clinical evolution (follow-up period > 12 months) and imaging test., Results: Prevalence of recurrence was 66.6 %. FDG-PET was positive in 40/60 patients, with confirmation in 39 cases, and 18 were true negative (TN). We have found 2 false positive and 1 false negative. Overall sensitivity, specificity, PPV, NPV and accuracy were 97.5 %, 90 %, 95.12 %, 94.7 % and 95 %, respectively. FDG-PET changed the modality of treatment in 34 patients (clinical impact 56.6 %), Conclusions: FDG-PET has high clinical impact in patients with suspicion of recurrent head and neck cancer, and should be incorporated in the diagnostic protocols before making a therapy decision.

Unlabelled: This study aimed to evaluate the role of Fluorine-18-fluorodeoxyglucose positron emission tomography (PET-FDG) in patients with elevated serum thyroglobulin (hTg) levels where thyroid cancer tissue does not concentrate radioiodine, rendering false-negative results on I-131 scanning., Material and Methods: Whole-body PET imaging using FDG was performed in 54 patients (37 female, 17 male) aged 17-88 years: 45 with papillary tumors and 9 with follicular tumors who were suspected of having recurrent thyroid carcinoma due to elevated thyroglobulin levels (hTg > 2 ng/ml) under thyroid-stimulating hormone (TSH > or = 30 microIU/ml) in whom the iodine scan was negative. All whole body scans were obtained with diagnostic doses (185 MBq). Whole body PET imaging was performed in fasting patients following i.v. administration of 370 MBq FDG while the patients were receiving full thyroid hormone replacement. Before PET, 99mTc methoxyisobutylisonitrile scintigraphy (99mTc-MIBI) was done in 14 patients and morphologic imaging in 26 by CT scan., Results: Positive PET results confirmed the presence of hypermetabolic foci in 25/54 patients (46.29 %). Positive findings were found for PET-FDG in patients with hTg levels higher than 10 ng/ml receiving full thyroid hormone replacement. 99mTc-MIBI demonstrated lesions in 7/14 patients (50 %). PET-FDG and 99mTc-MIBI had congruent positive results in 4/7 patients. All the lesions found by CT were detected by PET-FDG, while recurrent disease was found in 12/21 patients with previous negative CT., Conclusions: These results suggest that PET-FDG seems to be a promising tool in the follow-up of thyroid cancer and should be considered in patients suffering from differentiated thyroid cancer with suspected recurrence and/or metastases by elevated thyroglobulin levels, and negative I-131 whole body scans. PET-FDG might be more useful at hTg levels > 10 ng/ml.