P. Paulus

Oncological Applications of Positron Emission Tomography with Fluorine-18 Fluorodeoxyglucose

Positron emission tomography (PET) is now primarily used in oncological indication owing to the successful application of fluorine-18 fluorodeoxyglucose (FDG) in an increasing number of clinical indications at different stages of diagnosis, and for staging and follow-up. This review first considers the biological characteristics of FDG and then discusses methodological considerations regarding its use. Clinical indications are considered, and the results achieved in respect of various organs and tumour types are reviewed in depth. The review concludes with a brief consideration of the ways in which clinical PET might be improved.

Evaluation of the solitary pulmonary nodule by positron emission tomography imaging

Current noninvasive imaging methods are not sufficiently reliable for accurate detection of malignancy in most solitary pulmonary nodules (SPNs). Positron emission tomography (PET) using 18-fluorodeoxyglucose (FDG), showing increased FDG uptake and retention in malignant cells, has proved useful to differentiate malignant from benign tissue and could, therefore, contribute to the evaluation of the SPN. We performed a prospective study of 50 patients referred to the Pneumology Department with unclear diagnoses of SPN after conventional radiological screening. PET study was performed on each subject before an invasive procedure was proposed. Thirty three patients had a malignant nodule and 17 had a benign nodule. The mean size of malignant nodule was 3 cm (range 1.5-4.5 cm). All showed a marked increase in 18-FDG uptake. The mean size of benign nodule was 1.8 cm (range 0.5-3.5 cm). PET imaging showed the absence of 18-FDG uptake and correctly identified 15 of 17 benign nodules. There was two false-positive cases with a moderate increase in 18-FDG uptake (1 postprimary tuberculosis; and 1 anthracosilicotic nodule with nonspecific inflammation). At present, the sensitivity and specificity of the method are 100 and 88%, respectively. The positive and negative predictive values of PET imaging for SPNs are 94 and 100%, respectively. Our preliminary results demonstrate that PET-FDG imaging is a noninvasive technique, which appears highly accurate in differentiating malignant SPN from benign SPN.

Whole-Body 18f-Fdg Pet for the Evaluation of Patients with Hodgkin's Disease and Non-Hodgkin's Lymphoma

Whole-body metabolic information provided by 18F-FDG PET could help in the evaluation of lymphoma patients at diagnosis and follow-up. We studied 60 patients, 42 at initial presentation and 18 for disease recurrence (23 aggressive non-Hodgkins lymphoma, 21 low-grade non-Hodgkins lymphoma and 16 Hodgkins disease). All patients underwent a clinical examination, computed tomography (CT) and a non-attenuated PET scan within 1 week. The patients received 222-296 MBq (6-8 mCi) 18F-FDG intravenously and emission scans were recorded 45-90 min later. 18F-FDG PET detected more lymph nodes than the clinical examination or CT, but this rarely resulted in upstaging (two patients). The concordance between PET and CT for the evaluation of the spleen, liver and digestive tract was quite good. Discordance was noted in 12 patients for the evaluation of bone marrow infiltration, but confirmation by MRI or focal biopsy was not always obtained. We conclude that non-attenuated 18F-FDG PET is an easy and efficient whole-body method for the evaluation of patients with lymphomas. Compared with conventional techniques, however, it does not appear to offer much improvement for staging but provides a satisfactory base for follow-up.

Whole-body 18FDG positron emission tomography in the staging of non-small cell lung cancer

Despite advances in morphological imaging, some patients with lung cancer are found to have nonresectable disease at surgery or die of recurrence within yr of surgery. We performed a prospective study in 109 patients to compare the accuracy of whole-body positron emission tomography (PET) using fluorine-18 deoxyglucose (18FDG) and conventional imaging (CI) methods for the staging of non-small cell lung cancer (NSCLC). When CI or PET study suggested metastatic disease, confirmation was obtained by biopsy or follow-up information. As compared to CI, 18FDG-PET correctly changed the N stage in 22 patients (33%) and the M stage in 15 patients (14%). For the detection of distant metastases, PET study showed five false-positive sites and no false-negative cases. Currently, the accuracy of PET in the detection of M stage is 96%. Our study shows that visual interpretation of whole-body fluorine-18 deoxyglucose-positron emission tomography images can improve the diagnostic accuracy in the staging of non-small cell lung cancer. Further experience is needed to establish if metabolic imaging would be a cost-effective tool in the future management of lung cancer.

18fdg-Pet for the Assessment of Primary Head and Neck Tumors: Clinical, Computed Tomography, and Histopathological Correlation in 38 Patients

Objectives: To evaluate the clinical usefulness of FDG‐PET (fluoro‐2‐deoxy‐glucose‐positron emission tomography) in the detection of lymph node involvement and recurrences in patients with head and neck cancer. Study Design: Retrospective review of 38 patients with biopsy‐proven head and neck cancers who underwent clinical, computed tomography (CT), and FDG‐PET examinations. Twenty‐five patients were studied prior to therapy and 13 patients were evaluated for disease recurrence. Methods: All patients were operated and clinical data, CT, and FDG‐PET results were correlated with histopathological findings. Results: All primary tumors in 25 patients were detected, with the exception of one small superficial localization of the epiglottis. Histopathological examination showed lymph node involvement in 10 patients; PET detected lymph node involvement in five. FDG‐PET found one case of nodal disease not identified by clinical and CT examination. With so few cases, this could be anecdotal. Five false‐negative results (microscopic lymph node involvement) and two false positives were noted. Twelve of 13 patients with recurrent disease were correctly identified with FDG‐PET. FDG‐PET was the only imaging technique to identify local recurrence in two patients and lymph node involvement in two others. One false‐positive result occurred in a patient with a foreign body granuloma. Conclusions: FDG‐PET is a useful diagnostic modality for the detection of recurrent tumors and, in selected cases, precise lymph node involvement. The best way to further investigate the utility of clinical FDG‐PET is in the follow‐up of treated patients. Key Words: FDG‐PET, head and neck cancer, lymph node metastases, recurrent disease. Laryngoscope, 108:1578–1583, 1998

Staging of the mediastinum: value of positron emission tomography imaging in non-small cell lung cancer

Recent studies have shown limitations of morphological imaging in staging mediastinal lymph node involvement in lung cancer. In contrast to computed tomography (CT), which depends primarily on anatomical imaging features, positron emission tomography (PET) with 18-fluorodeoxyglucose (FDG) depends mainly on the metabolic characteristics of a tissue for the diagnosis of disease. We have performed a prospective study comparing FDG-PET and CT of the thorax in the presurgical assessment of the mediastinum in 50 patients with newly diagnosed non-small cell lung cancer (NSCLC). CT and PET scans were interpreted separately, and results were compared to pathological staging obtained during thoracotomy. Hilar or mediastinal lymph node involvement was present in 58%. In staging for lymph node involvement, CT had a sensitivity of 72% and specificity of 81%, whereas PET had a sensitivity and specificity of 90% and 86%, respectively. When the PET study was compared to histological results, there were four cases showing more advanced mediastinal involvement with PET and four cases showing less involvement with PET. From our preliminary results, we conclude that positron emission tomography with 18-fluorodeoxyglucose is significantly more accurate than computed tomography in the mediastinal staging of non-small cell lung cancer.

Clinical evaluation of whole-body 18F-fluorodeoxyglucose positron emission tomography in the detection of liver metastases

BACKGROUND Assessment of metastatic involvement of the liver remains a diagnostic challenge. The objective of this study was to evaluate the potential role of FDG PET in the detection of liver metastases. PATIENTS AND METHODS Sixty-four patients with malignancy and possible liver involvement were included. Liver metastases were present in 31 cases, demonstrated by histopathological analysis in 15 cases and by follow-up in 16 cases. The negative cases were confirmed by pathology in four cases, peroperative ultrasonography in 12 cases, and follow-up in 17 cases. Whole-body FDG PET was compared to CT (n = 53) and US (n = 43). RESULTS PET demonstrated a 97% sensitivity, an 88% specificity and a 92% accuracy, compared to 93%, 75% and 85%, respectively, for CT (P = NS). Concordant results were obtained in 44 of 64 patients (69%: 19 TP. 25 TN). PET provided new and accurate information in 15 of 64 patients (23.4%). PET demonstrated liver metastases in 11 patients in whom conventional methods yielded negative (two cases) or doubtful (nine cases) results. Four patients free of liver involvement were correctly staged with PET, while CT/US were equivocal. PET was erroneous in five of 64 cases (7.8%, four FP, one FN). CONCLUSIONS FDG PET allows an accurate screening of liver involvement in patients with malignancy. Combined with CT, it provides additional diagnostic information that could directly affect the management of these patients.

Staging of non-small-cell lung cancer by whole-body fluorine-18 deoxyglucose positron emission tomography

Positron emission tomography (PET) using fluorine-18 deoxyglucose (FDG), showing increased FDG uptake and retention in malignant cells, has been proven useful to differentiate malignant from benign tissue. We undertook a prospective study in 61 patients to compare the accuracy of whole-body FDG PET and conventional imaging (CI) methods for the staging of nonsmall-cell lung cancer (NSCLC). CI included chest and abdomen computed tomographic scanning and bone scintigraphy. When CI or PET study suggested metastatic disease, confirmation was obtained by biopsy or clinical or radiological follow-up. As compared to CI, PET correctly changed the N stage in 13 patients (21%) and the M stage in six patients (10%). There were three false-positive and no false-negative distant PET findings. Our preliminary results show that whole-body FDG PET can improve the diagnostic accuracy in the staging of NSCLC.

Intérêt de la tomographie à émission de positrons dans l’évaluation des tumeurs gastro-intestinales

RésuméLa TEP au 18FDG présente de nombreuses indications dans l’évaluation des tumeurs digestives. Son rôle principal concerne le bilan d’extension des récidives tumorales démontrées ou suspectées mais des indications plus ponctuelles concernent également le diagnostic différentiel des masses pancréatiques et le bilan initial du cancer de l’œsophage. Le principal avantage de la TEP résulte de la nature métabolique du signal, indépendant et complémentaire des modifications anatomiques visibles en imagerie classique. Un autre avantage est lié à l’examen du corps entier aujourd’hui pratiqué systématiquement. La TEP trouve dès lors sa place en première ligne dans ses différentes indications.SummaryPET with 18-FDG has numerous indications in the evaluation of patients with gastrointestinal carcinoma. Its principal indications are the staging of suspected or demonstrated recurrent disease and to assess the operability of lesion. Validated indications also concern the differential diagnosis of pancreatic masses and the initial staging of oesophageal cancer.The metabolic signal of PET constitutes its main advantage. It is independent but complementary to the anatomical changes assessed by structural imaging. Another advantage is related to imaging of the whole-body is now routinely performed. PET can thus be a one step examination in the staging of digestive cancers and is best used early in the staging process.