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The aim of this multicentre study was to evaluate the clinical significance of fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in differentiated thyroid carcinoma and to compare the results with both iodine-131 whole-body scintigraphy (WBS) and technetium-99m 2-methoxyisobutylisonitrile (MIBI) or thallium-201 chloride (Tl) scintigraphy. Whole-body PET imaging using FDG was performed in 222 patients: 134 with papillary tumours, 80 with follicular tumours and 8 with mixed-cell type tumours. Finally, for each case an overall clinical evaluation was done including histology, cytology, thyroglobulin level, ultrasonography, computed tomography and subsequent clinical course, to allow a comparison with functional imaging results. Sensitivity of FDG-PET was 75% and 85% for the whole patient group (n = 222) and the group with negative radioiodine scan (n = 166), respectively. Specificity was 90% in the whole patient group. Sensitivity and specificity of WBS were 50% and 99%, respectively. When the results of FDG-PET and WBS were considered in combination, tumour tissue was missed in only 7%. Sensitivity and specificity of MIBI/Tl were 53% and 92%, respectively (n = 117). We conclude that FDG-PET is a sensitive method in the follow-up of thyroid cancer which should be considered in all patients suffering from differentiated thyroid cancer with suspected recurrence and/or metastases, and particularly in those with elevated thyroglobulin values and negative WBS.

FDG PET has the potential to improve the detection of lymphadenopathy and the differential diagnosis of pancreatic masses.

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Summary:We investigated the predictive value of sequential FDG PET before and after high-dose chemotherapy (HDT) and autologous stem cell transplantation (ASCT) in 24 patients suffering from non-Hodgkin's lymphoma (NHL). FDG PET was performed at baseline, after three cycles of induction therapy, before and after HDT with ASCT. Response assessment from sequential PET scans using standardized uptake values (SUV) was available in 22 patients at the time of transplantation. Partial metabolic response (PMR) was defined as a Ͻ25% decrease of SUV between successive PET scans. Six of seven patients who did not achieve a PMR after complete induction therapy developed lymphoma progression, while 10 of 15 patients with complete metabolic response (CMR) or PMR remained in continuous remission. Four of seven patients with less than PMR after induction therapy died vs two of 15 patients with CMR/PMR. Median progression-free and overall survival of patients with less than PMR after HDT and ASCT was 9 and 29 months, respectively. In contrast, neither conventional re-staging nor the International Prognostic Index were predictive. These data suggest that sequential quantitative PET imaging does enlarge the concept of chemosensitivity used to select patients with high-risk NHL for HDT and ASCT or to route them to alternative treatments. High-dose chemotherapy (HDT) with autologous stem cell transplantation (ASCT) has been shown to be the best available treatment in patients who have relapsed from nonHodgkin's lymphoma (NHL) after conventional chemotherapy, but who remained chemotherapy-sensitive.1 This has prompted the use of HDT with ASCT as a front-line therapy in patients with high-intermediate or high risk disease according to the International Prognostic Index.2 However, clinical results have been discrepant and additional prognostic factors are needed to predict final outcome of the patients at the time of transplantation.Positron emission tomography (PET) using the glucose analogue fluorine-18-fluorodeoxglucose (FDG) has been demonstrated to improve primary staging of lymphoma and to be more precise than conventional radiological imaging for re-staging after chemotherapy.3-7 Several groups including our own have reported the high predictive value of persisting abnormal FDG uptake for residual or recurrent disease in this context. 7-9Thus FDG-PET does have a potential role in the identification of patients requiring further intensified chemotherapy. Moreover, FDG-PET can be used as a functional and quantitative measure of tumor response to induction chemotherapy 10 and may be able to differentiate between responders and non-responders at an earlier time-point than conventional CT or MRI imaging. Preliminary results in a small patient population studied before onset of treatment and again after one and two chemotherapy cycles support this hypothesis. 11We prospectively enrolled consecutive patients with NHL who were scheduled for HDT including ASCT. Progression-free and overall survival were chosen as end points of the study....