Clinical impact of fluorine-18 fluorodeoxyglucose positron emission tomography in cancer patients. A comparative study between dedicated camera and dual-head coincidence gamma camera.

AIM: Positron emission tomography (PET) using fluorine-18 fluorodeoxyglucose (FDG) can be performed using a dedicated PET scanner (PET-I) or a dual-head coincidence gamma camera (CGC-I). The aim of this study was to comparatively assess the impact of PET-I and CGC-I on clinical management in cancer patients. METHODS: From November 2000 to November 2002, PET-I and CGC-I were performed at an interval of 2 days in 151 patients with colorectal cancer (n=40), breast cancer (n=28), thyroid cancer (n=23), lung tumors (n=22), germ cell tumors (n=14), unknown primary cancer (n=7) and other cancers (n=17). PET-I and CGC-I were interpreted independently with knowledge of conventional imaging (CI). In June 2003, theoretical management, e.g. treatment modality/ies and treatment intent (curative or palliative), after CI, PET-I and CGC-I were stated during multidisciplinary sessions and were a posteriori considered as appropriate or inappropriate using pathological and follow-up data. RESULTS: The theoretical management proposed after PET-I and after CGC-I was similar in 112/151 (74%; 95% CI: 66-81%) patients. In 125 assessable patients, theoretical management after PET-I was appropriate in 86% (95% CI: 79-92%), significantly higher (P=0.0033) than after CGC-I (70%; 95% CI: 62-78%). Both proportions were also higher than after CI (46%; 95% CI: 37-56%), (P<0.0001). A similar trend for higher proportions of appropriate management after PET-I than after CGC-I was observed for each tumor localization. CONCLUSIONS: The clinical impact of PET-I is superior to that of CGC-I in a large series of cancer patients. Although CGC-I could be considered as an acceptable alternative, PET-I remains the standard and should preferably equip nuclear medicine departments.

Non-invasive grading of oligodendrogliomas: correlation between in vivo metabolic pattern and histopathology.

Several studies have shown that the prognosis of oligodendrogliomas is dependent on their histological grade. In order to identify a non-invasive method for the primary diagnosis and follow-up of these tumours, we investigated the relationship between their in vivo metabolism, assessed by positron emission tomography (PET), and their histological grade assessed at the same time. Forty-seven patients with histologically confirmed oligodendrogliomas were investigated. Conventional neuroradiological assessment by computed tomography and magnetic resonance imaging (MRI) was performed in all the patients. All the histology slices were reviewed by the same pathologist after referral from various pathology laboratories. The PET investigation included a carbon-1 methionine (11C-MET) uptake study and, in the majority of cases, a fluorine-18 fluorodeoxyglucose (18F-FDG) uptake study, in order to investigate at the same time both amino acid metabolism and glycolysis. The sampled tumour region of interest (ROI) was defined from the T1-weighted 3D MR scan matched with the PET scan. Tracer concentration in each voxel of the tumour ROI was divided by the mean concentration in an ROI of the same size located in the healthy brain tissue. For each tumour and each tracer, we characterized the metabolic pattern on the basis of the mean and the maximum tumour to healthy tissue concentration ratio, and also the standard deviation and range of the ratios, which indicate the degree of metabolic heterogeneity of the tumour. The histological criteria for differentiating between high- and low-grade tumours were those of the WHO and, partially, of the Sainte-Anne-Daumas-Duport classification. Highly significant differences between high- and low-grade oligodendrogliomas (Mann-Whitney test: P<0.0001) were observed for all the assessed parameters of 11C-MET uptake. On the other hand, the pattern of 18F-FDG uptake showed only moderate differences between the two tumour groups.