Whole-body [18F]FDG PET in the management of metastatic brain tumours

BACKGROUND: To determine its roles in the diagnosis and the systemic evaluation of metastatic brain tumours, whole-body positron emission tomography (PET) using [18F]FDG was performed in 20 consecutive patients. METHODS: All patients were thought to be suffering or needing to be differentiated from metastatic brain tumours. Nine patients had multiple brain lesions; six were older and showed a rim-enhancing lesion with surrounding oedema; seven had homogeneously enhancing periventricular lesion(s) on computed tomography (CT) and/or magnetic resonance (MR) imaging, thought to be central nervous system lymphomas. Two patients had skull mass(es) and two patients had a solid mass suspected to be, respectively, a haemorrhagic metastasis and a metastatic malignant melanoma. All of them received whole-body [18F]FDG PET and conventional systemic work-up for metastasis in order to compare the results of the two methods. RESULTS: Metastatic brain tumours were diagnosed on whole-body [18F]FDG PET in eleven patients who had extracranial and intracranial hypermetabolic lesions. In nine of these, a conventional work-up also detected primary lesions which on whole-body [18F]FDG PET were seen to be hypermetabolic foci. Systemic lymph node metastases were detected by whole-body [18F]FDG PET only in two patients and histological diagnosis was possible by biopsy of lymph nodes rather than of brain lesions. In the remaining nine patients who had only intracranial hypermetabolic foci, histological diagnosis was made by craniotomy or stereotactic biopsy. It was confirmed that seven of nine patients were suffering from a primary brain tumour and two from metastatic carcinoma. None of the nine showed evidence of systemic cancer on conventional work-up. Histological diagnoses of the primary brain tumours were four cases of primary central nervous system lymphoma and one each of multifocal glioblastoma, Ewing's sarcoma, and cavernous angioma. Patients felt no discomfort during the whole-body [18F]FDG PET procedure and there were no complications. The false negative rate in [18F]FDG PET and in conventional work-up was 15.4% and 30.7% respectively. There were no false positives on either [18F]FDG PET or conventional work-up. CONCLUSION: It is suggested that whole-body [18F]FDG PET is a safe, reliable, and convenient method for the diagnosis and systemic evaluation of patients thought to be suffering or needing to be differentiated from a metastatic brain tumour.     

Detection of extrathoracic metastases by positron emission tomography in lung cancer

BACKGROUND: Accurate staging of non-small cell lung cancer is essential for treatment planning. We evaluated in a prospective study the role of whole-body 2-[18F]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) in mediastinal nodal staging with a positive predictive value of 96%. The study was continued to further evaluate the value of whole-body FDG PET in detecting unexpected extrathoracic metastases (ETMs) in patients qualifying for surgical treatment by conventional staging. METHODS: One hundred patients underwent clinical evaluation, chest and upper abdominal computed tomography scan, mediastinoscopy (lymph nodes greater than 1 cm on computed tomography), and routine laboratory tests. In 94 patients with stage IIIa or less and 6 with suspected N3 a whole-body FDG PET was performed. If clinical signs of ETMs were present additional diagnostic methods were applied. All findings in the FDG PET were confirmed histologically or radiologically. RESULTS: Unexpected ETMs were detected in 13 (14%) of 94 patients (stage IIIa or less) at 14 sites. In addition 6 of 94 patients were restaged up to N3 after PET. The suspected N3 disease (stage IIIb) on computed tomography was confirmed by PET in all 6 patients. There was no false positive finding of ETM. Weight loss was correlated with the occurrence of ETM: more than 5 kg, 5 of 13 patients (38%); more than 10 kg, 4 of 6 patients (67%). Pathologic laboratory findings were not predictive for ETM. CONCLUSIONS: Whole-body FDG PET improves detection of ETMs in patients with non-small cell lung cancer otherwise elegible for operation. In 14% of patients (stage IIIa or less), ETMs were detected, and in total, 20% of the patients were understaged.     

Detection of paraneoplastic anti-neuronal autoantibodies on paraffin-embedded tissues

Although the detection of pancreatic carcinoma has been considerably improved by recently developed imaging procedures, differential diagnosis between cancer and benign tumor masses, as well as lymph node staging, is still difficult. In vivo evaluation of regional glucose metabolism by means of positron emission tomography (PET) and fluorine-18-labelled fluorode-oxyglucose (FDG) is a new approach utilizing metabolic instead of morphological tumor properties for diagnosis. PATIENTS AND METHODS. A total of 85 patients with suspected pancreatic carcinoma were investigated by FDG-PET prior to surgery. Static PET scans were evaluated visually as well as quantitatively, taking increased FDG uptake as a sign of malignancy. PET results were correlated with intraoperative findings and histopathology of surgical specimens. RESULTS. Forty-seven out of 55 (85%) malignant tumors and 23 out of 30 (77%) benign lesions were correctly classified by PET. Lymph node metastases were present in 31 patients, 19 of them (61%) positive in PET. In 7 our of 13 (54%) patients with liver metastases, PET detected hypermetabolic lesions. False-negative findings were mainly due to disturbance of glucose metabolism in diabetic patients, while most false-positive results could be attributed to acute inflammatory lesions in chronic pancreatitis. CONCLUSIONS. Our results indicate that classification of pancreatic masses can be improved by use of FDG-PET, which might lead to a reduction of unnecessary laparotomies in patients with benign or incurable disease.     

Lesion-to-background ratio in nonattenuation-corrected whole-body FDG PET images

The purpose of this study was to compare the diagnostic efficacy of attenuation-corrected and nonattenuation-corrected whole-body 18F-fluorodeoxyglucose (FDG) PET images to determine an adequate method that can semiquantitatively evaluate nonattenuation-corrected images. METHODS: Whole-body PET studies were performed in 24 fasting patients with various tumors (lung cancers, n = 18; mediastinal tumors, n = 4; breast cancers, n = 2) 30-40 min after a bolus injection of 18F-FDG. Transmission scans followed emission data acquisition. Reconstructed attenuation-corrected and uncorrected images were displayed simultaneously and the relative FDG uptake in lesions and corresponding background areas was evaluated by the region of interest method. Both types of images were also compared with X-CT scans and conventional nuclear medicine scans for diagnostic efficacy. RESULTS: Attenuation-corrected and uncorrected images were found to be equally sensitive for detecting lesions. There was a strong linear correlation between lesion-to-background (L/B) ratios calculated on attenuation-corrected and uncorrected images (r = 0.98; p < 0.001). Significant differences in L/B ratios between attenuation-corrected and uncorrected images were present in only 6 of 55 lesions (11%). Standardized uptake ratios (SURs) in attenuation-uncorrected images did not correlate with SURs in attenuation-corrected images nor with L/B ratios in uncorrected images. CONCLUSION: The efficacy of attenuation-uncorrected FDG PET images in evaluating tumors is similar to that using attenuation-corrected images. Uncorrected images provide not only clinically useful but also quantitative information equivalent to that provided by attenuation-corrected images. However the L/B ratio is the only available index that can be used for quantification of uncorrected images.     

Controlled prospective study of positron emission tomography using the glucose analogue [18f]fluorodeoxyglucose in the evaluation of pulmonary nodules

BACKGROUND: Positron emission tomography (PET) is a new imaging technique which, by measuring focal metabolic activities, can make a qualitative statement (benign or malignant) about a tumour. PET has been described in many studies to provide a high diagnostic accuracy for the evaluation of pulmonary coin lesions. However, these studies were not always supported by histological confirmation of the results. In a controlled prospective study, it was investigated whether the diagnostic accuracy of PET is sufficiently high to allow omission of diagnostic thoracotomy or thoracoscopy in the case of a negative finding. METHODS: A PET scan was carried out before operation using [18F]fluorodeoxyglucose (FDG) in 50 patients with pulmonary coin lesions (diameter 30 mm or less). All of these lesions were completely removed thoracoscopically or by a formal thoracotomy and were examined histologically. Using the histology results, the diagnostic accuracy of the PET procedure with regard to a benign or malignant diagnosis was evaluated and compared with that of computed tomography (CT). Results From a total of 54 coin lesions (four of the 50 patients had two lesions) there were 31 malignant (19 primary bronchial carcinomas, 12 metastases) and 23 benign diagnoses. With the PET procedure 28 of 31 malignant and 19 of 23 benign lesions were classified correctly (sensitivity 90 per cent, specificity 83 per cent). False negatives included two bronchial carcinomas and one metastasis. CT had a sensitivity of 100 per cent and specificity of 52 per cent. CONCLUSION: FDG PET cannot generally be considered as a replacement for diagnostic thoracoscopy or thoracotomy at the present time. However, by combining FDG PET with radiological follow-up, clinical applications may evolve in patients at low risk for a malignant tumour or at high risk for surgical complications.     

Computed tomography and positron emission tomography in the pre-operative staging of oesophageal carcinoma

Because patients with carcinoma of the oesophagus usually present with advanced disease and surgery has a high mortality with cure in less than 10% of patients, pre-operative staging to select appropriate patients is necessary. Computed tomography (CT) plays an important role in staging but has well recognized limitations. Positron emission tomography (PET) which provides physiological information may therefore be a better alternative. OBJECTIVE: To compare the findings of CT and positron emission tomography (PET) with 2-[18fluorine]-fluoro-2-deoxy-D-glucose (FDG) in the pre-operative staging of oesophageal carcinoma. MATERIALS AND METHODS: Twenty-five patients with biopsy proven oesophageal cancer had pre-operative staging using CT and FDG-PET. The studies were read independently and full histological confirmation was obtained in 19 patients. Four parameters were studied: the primary tumour, peri-oesophageal lymph nodes, liver metastases and left gastric lymph nodes. RESULTS: PET visualized all primary tumours; CT missed one. CT identified 4/8 patients with involved peri-oesophageal nodes and PET 3/8. CT identified 5/9 patients with left gastric adenopathy and PET 1/9. PET visualized a liver metastasis missed on CT and appeared to be better in assessing residual tumour. PET did identify distant metastases not seen on CT in seven patients. CONCLUSIONS: The two techniques are both effective in showing the primary tumour and about equally sensitive in the demonstration of peri-oesophageal nodes. PET is probably more sensitive than CT for the detection of distant metastases.     

FDG PET and dual-head gamma camera positron coincidence detection imaging of suspected malignancies and brain disorders

The purpose of the study was to compare the diagnostic accuracy of fluorodeoxyglucose (FDG) images obtained with a dual-head coincidence gamma camera (DHC) with those obtained with a dedicated PET in a series of 26 patients. METHODS: Nineteen patients with known or suspected malignancies and 7 patients with neurological disorders underwent PET imaging after injection of approximately 10 mCi of FDG. Whole-body imaging was performed on 19 patients and brain imaging on 7 patients. DHC images were then acquired for 30 min over the region of interest using a dual-head gamma camera equipped with 3/8-in.-thick NaI(TI) crystals and parallel slit-hole collimators. The images were reconstructed in the normal mode, using photopeak/photopeak, photopeak/Compton and Compton/photopeak coincidence events. RESULTS: Although the spatial resolutions of PET with a dedicated PET scanner and of DHC are in the same range, the lesion detectability remains superior with PET (4 mm for PET versus 13.5 mm for DHC in phantom experiments) with a contrast ratio of 5:1. This is most probably attributable to the higher sensitivity of PET (2238 coincidences/min/microCi for PET versus 89 coincidences/min/microCi for DHC). The pattern of uptake and interpretation for brain imaging was similar on both PET and DHC images in all patients. In the 19 oncology patients, 38 lesions ranging from 0.7 to 5 cm were detected by PET. DHC imaging detected 28 (73%) of these lesions. Among the 10 lesions not seen with DHC, 5 were less than 1.2 cm, 2 were located centrally within the liver and suffered from marked attenuation effects and 3 were adjacent to regions with high physiological activity. The nondetectability of some lesions with DHC compared with PET can be explained by several factors: (a) start of imaging time (mean+/-SD: 73+/-16 min for PET versus 115+/-68 min for DHC, leading to FDG decay to 6.75 mCi for PET and 5.2 mCi for DHC); (b) limited efficiency of a 3/8-inch-thick Nal(TI) crystal to detect 18F photons; (c) suboptimal two-dimensional reconstruction algorithm; and (d) absence of soft-tissue attenuation correction for centrally located lesions. CONCLUSION: FDG DHC imaging is a promising technique for oncological and brain imaging.     

F-18 FDG whole-body positron emission tomography scan in primary breast sarcoma

Three patients with primary breast sarcoma showed intense F-18 FDG breast uptake on the whole-body scan. In two patients the uptake was irregular and associated with cold foci that corresponded to hypodense lesions noted on the chest CT; these represented areas of pathologically demonstrated tumor necrosis. There was also intense FDG uptake in pulmonary, axillary, and supraclavicular lymph node metastases. All lesions were confirmed by CT scan of the chest. Thus F-18 FDG positron emission tomographic scanning accurately staged the tumors in these two patients, and it documented local recurrence in the third patient. Histopathologic examination showed evidence of a high-grade sarcoma, a primary rhabdomyosarcoma, and a malignant cystosarcoma phyllodes of the breast. Similar to breast carcinoma, F-18 FDG whole-body positron emission tomographic imaging could be useful in diagnosing and staging primary breast sarcomas.     

Evaluation of benign vs malignant hepatic lesions with positron emission tomography

BACKGROUND: In most malignant cells, the relatively low level of glucose-6-phosphatase leads to accumulation and trapping of [18F]fluorodeoxyglucose (FDG) intracellularly, allowing the visualization of increased uptake compared with normal cells. OBJECTIVES: To assess the value of FDG positron emission tomography (PET) to differentiate benign from malignant hepatic lesions and to determine in which types of hepatic tumors PET can help evaluate stage, monitor response to therapy, and detect recurrence. DESIGN: Prospective blinded-comparison clinical cohort study. SETTING: Tertiary care university hospital and clinic. PATIENTS: One hundred ten consecutive referred patients with hepatic lesions 1 cm or larger on screening computed tomographic (CT) images who were seen for evaluation and potential resection underwent PET imaging. There were 60 men and 50 women with a mean (+/-SD) age of 59 +/- 14 years. Follow-up was 100%. INTERVENTIONS: A PET scan using static imaging was performed on all patients. The PET scan imaging and biopsy, surgery, or both were performed, providing pathological samples within 2 months of PET imaging. All PET images were correlated with CT scan to localize the lesion. However, PET investigators were unaware of any previous interpretation of the CT scan. MAIN OUTCOME MEASURES: Visual interpretation, lesion-to-normal liver background (L/B) ratio of radioactivity, and standard uptake value (SUV) were correlated with pathological diagnosis. RESULTS: All (100%) liver metastases from adenocarcinoma and sarcoma primaries in 66 patients and all cholangiocarcinomas in 8 patients had increased uptake values, L/B ratios greater than 2, and an SUV greater than 3.5. Hepatocellular carcinoma had increased FDG uptake in 16 of 23 patients and poor uptake in 7 patients. All benign hepatic lesions (n = 23), including adenoma and fibronodular hyperplasia, had poor uptake, an L/B ratio of less than 2, and an SUV less than 3.5, except for 1 of 3 abscesses that had definite uptake. CONCLUSIONS: The PET technique using FDG static imaging was useful to differentiate malignant from benign lesions in the liver. Limitations include false-positive results in a minority of abscesses and false-negative results in a minority of hepatocellular carcinoma. The PET technique was useful in tumor staging and detection of recurrence, as well as monitoring response to therapy for all adenocarcinomas and sarcomas and most hepatocellular carcinomas. Therefore, pretherapy PET imaging is recommended to help assess new hepatic lesions.     

Role of superoxide dismutase in ischemic brain injury: a study using SOD-1 transgenic mice

In 1991, this prospectively designed study was started to assess the potentials of positron emission tomography with 18FDG in the diagnostic workup for the detection of lymph node metastases in testicular cancer, since there were no data available concerning this subject at this time. In 54 patients (27 patients with pure seminoma, 27 patients with non-seminomatous tumors) 18FDG-PET results were compared with the findings obtained with abdominal computed tomography, serum level of tumor markers (AFP, beta-HCG), and the histopathological findings after primary or post-chemotherapy retroperitoneal lymph node dissection. In 21 patients with pure seminoma (clinical stage I according to the Lugano classification) 18FDG-PET results were identical with those of the abdominal computed tomography, so PET does not add relevant informations in this group of patients. In 7 patients presenting with non-seminomatous testicular cancer (stage I), PET was not able to detect the existing micrometastases in 4 patients. In 1/7 case PET examination showed a suspicious focal lesion, this lymph node had 2 micrometastases within inflammatory changes. In 1/7 patient 18FDG-PET definitely revealed metastatic lesions, while the CT scans where judged to be unobtrusive and tumor marker levels were within the normal range. In the 4 patients with pure seminomas stage II B and II C (N = 6), that have undergone retroperitoneal lymph node dissection following chemotherapy, 18FDG-PET correctly predicted absence of tumor in 3 out of these 4, and in 1/4 patient the benign nature of a persistent large tumor after two cycles of polychemotherapy was correctly identified which eventually turned out to be a ganglioneuroma. This lesion falsely was classified as malignant tumor with abdominal computed tomography, and in 2/4 patients post-chemotherapy residual retroperitoneal lesions in the CT scans could not be assessed exactly whether or not malignant tumor was present. In 20 patients presenting with non-seminomatous testicular cancer (stage II and III) 18FDG-PET was able to demonstrate therapeutic effects of chemotherapy by showing decreasing tracer activity in those regions, that had hypermetabolic foci prior to chemotherapy. It became evident in testicular cancer that there is a single entity which is not characterized by increased glucose metabolism, the mature teratoma. In lesions detected by abdominal computed tomography which do not present increased 18FDG uptake, mature teratoma as well as scar/necrosis or rare other tumors with normal glucose metabolism can be supposed, but additional characteristics based on different 18FDG uptake were not observed. In 1/20 case post-chemotherapy PET scan detected a hypermetabolic lesion, which was suspicious for metastatic spread, but in the histopathological examination this lesion was identified as inflammatory tissue reaction. Based on the data reported here in 18FDG-PET cannot be considered a standard diagnostic tool in the staging examinations in testicular cancer. It is of clinical relevance in patients who present residual tumor after chemotherapy. In this situation 18FDG-PET is helpful in deciding whether or not a residual mass post-chemotherapy contains active tumor. 18FDG-PET can not replace retroperitoneal lymph node dissection for staging purposes.     

Fluorine-18-fluorodeoxyglucose assessment of glucose metabolism in bone tumors

In our study, we investigate the glucose metabolism of various types of bone lesions with 18F-fluorodeoxyglucose (FDG) PET. METHODS: Twenty-six patients showing clinical and radiographic symptoms of a malignant bone tumor were included. Histological examination after the PET study revealed 19 malignant and 7 benign tumors. PET images were corrected for attenuation. Arterial blood samples were taken to establish the input function. The metabolic rate of glucose consumption (MRglc) was calculated for the whole tumor, for the 10 pixels with maximum activity and for contralateral normal muscle tissue. RESULTS: All lesions were clearly visualized with 18F-FDG PET except for a small infarction of the humerus. All the other lesions had increased glucose metabolism compared to surrounding and contralateral muscle tissue. Both maximum and average MRglc for benign, as well as malignant, lesions were significantly higher than for contralateral normal tissue. The maximum and average MRglc were not higher for malignant as opposed to benign lesions. There was a large overlap between the MRglc of benign and malignant lesions. CONCLUSION: Fluorine-18-FDG PET appears suitable to visualize bone tumors. With the quantification of glucose metabolism, it is not possible to differentiate between benign and malignant bone tumors. There does not seem to be a clear correlation between the MRglc and the biologic aggressiveness of the neoplasms.     

FDG-PET in the staging of malignant melanoma

Positron emission tomography (PET scanning) is a useful tool in staging of malignant melanoma. A radiolabelled glucoseanalogue can demonstrate changes in metabolism and thus identify malignancy in macroscopic unchanged structures. It is a non-invasive, fast method to identify especially visceral, still symptomless metastases. The patient can often be spared from mutilating surgery.     

Metastatic melanoma of unknown primary origin shows prognostic similarities to regional metastatic melanoma: recommendations for initial staging examinations

BACKGROUND: Metastatic melanoma of unknown primary origin accounts for approximately 2-6% of all melanoma cases. The prognostic significance of this diagnosis is still controversial. METHODS: Of 3258 patients with malignant melanoma recorded during the period 1976-1996, 2.3% had metastases of unknown primary origin. Anatomic distribution, clinical stage, and survival probabilities were evaluated. RESULTS: Thirty patients were classified as having cutaneous or subcutaneous in-transit metastases, and they showed a 5-year survival rate of 83%. Thirty-seven patients were classified as having lymph node metastasis, and their 5-year survival rate was 50%. Disseminated disease was diagnosed in only 8 patients, who had a median survival of 6 months. Comparison of survival probabilities for patients with in-transit metastases and unknown primary tumors with the probabilities for those with cutaneous primary tumors revealed a significant advantage for the former group. No significant differences were found for patients with lymph node metastasis when those with unknown primary tumors were compared with those who had cutaneous melanomas with regional lymph node metastasis. CONCLUSIONS: The clinical disease course of patients with metastatic melanoma of unknown primary origin is similar to that of patients with primary cutaneous melanoma when the same clinical stages of the disease are compared. Based on the assumption that the majority of regional metastases develop from completely regressed primary cutaneous melanoma, recommendations for initial staging examinations in patients with unknown primary tumors are given in this article.     

Whole-body 2-[18F]-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) for accurate staging of Hodgkin's disease

BACKGROUND: Staging of Hodgkin's disease (HD) is accomplished by a variety of invasive and non-invasive modalities. This prospective study was undertaken to investigate the value of whole-body positron emission tomography (PET) with 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) in defining regions involved by lymphoma compared with conventional staging methods in patients with HD. PATIENTS AND METHODS: Fourty-four newly diagnosed patients with HD underwent FDG-PET as part of their initial staging work-up. PET findings were correlated with findings of conventional staging including computed tomography, ultrasound, bone scanning, bone marrow biopsy, liver biopsy and laparotomy. When results of FDG-PET differed to those obtained by conventional methods reevaluation was performed by biopsy, if possible, or magnetic resonance imaging. RESULTS: The results of FDG-PET were compared with three hundred twenty-one conventional staging procedures performed in 44 patients. FDG-PET was positive in 38 of 44 (86%) patients at sites of documented disease. PET detected additional lesions in five cases previously not identified by conventional staging methods. In another case a nodal lesion suspect on CT was negative at FDG-PET and was settled as true negative by biopsy. As a consequence of PET findings five patients had to be upstaged and one patient had to be downstaged, resulting in changes in treatment strategy in all six cases (14%). FDG-PET failed to visualize sites of HD in four patients. In two of our patients a false positive PET result was obtained. CONCLUSIONS: Our data indicate that FDG-PET provides an imaging technique that appears to visualize involved lesions in most patients with HD and is useful in the management of these patients.     

Prospective comparison of 18F-FDG PET with conventional imaging modalities (CT, MRI, US) in lymph node staging of head and neck cancer

The aims of this study were to investigate the detection of cervical lymph node metastases of head and neck cancer by positron emission tomographic (PET) imaging with fluorine-18 fluorodeoxyglucose (FDG) and to perform a prospective comparison with computed tomography (CT), magnetic resonance imaging (MRI), sonographic and histopathological findings. Sixty patients with histologically proven squamous cell carcinoma were studied by PET imaging before surgery. Preoperative endoscopy (including biopsy), CT, MRI and sonography of the cervical region were performed in all patients within 2 weeks preceding 18F-FDG whole-body PET. FDG PET images were analysed visually and quantitatively for objective assessment of regional tracer uptake. Histopathology of the resected neck specimens revealed a total of 1284 lymph nodes, 117 of which showed metastatic involvement. Based on histopathological findings, FDG PET correctly identified lymph node metastases with a sensitivity of 90% and a specificity of 94% (P<10(-6)). CT and MRI visualized histologically proven lymph node metastases with a sensitivity of 82% (specificity 85%) and 80% (specificity 79%), respectively (P<10(-6)). Sonography revealed a sensitivity of 72% (P<10(-6)). The comparison of 18F-FDG PET with conventional imaging modalities demonstrated statistically significant correlations (PET vs CT, P = 0.017; PET vs MRI, P = 0.012; PET vs sonography, P = 0.0001). Quantitative analysis of FDG uptake in lymph node metastases using body weight-based standardized uptake values (SUVBW) showed no significant correlation between FDG uptake (3.7+/-2.0) and histological grading of tumour-involved lymph nodes (P = 0.9). Interestingly, benign lymph nodes had increased FDG uptake as a result of inflammatory reactions (SUVBW-range: 2-15.8). This prospective, histopathologically controlled study confirms FDG PET as the procedure with the highest sensitivity and specificity for detecting lymph node metastases of head and neck cancer and has become a routine method in our University Medical Center. Furthermore, the optimal diagnostic modality may be a fusion image showing the increased metabolism of the tumour and the anatomical localization.     

Detection of bone metastases in breast cancer by 18FDG PET: differing metabolic activity in osteoblastic and osteolytic lesions

PURPOSE: 99mTechnetium methylene diphosphonate (99mTc MDP) bone scintigraphy is currently the method of choice for the detection of bone metastases, but 18F-fluoro-deoxy-D-glucose positron emission tomography (18FDG PET) offers superior spatial resolution and improved sensitivity. We have compared 18FDG PET with 99mTc MDP bone scintigraphy in patients with skeletal metastases from breast cancer and have analyzed the data in subgroups based on radiographic characteristics of lesions. PATIENTS AND METHODS: Twenty-three women with breast cancer and confirmed bone metastases were studied with both 99mTC MDP bone scintigraphy and 18FDG PET, and the number of lesions detected and the quantitation of uptake (standardized uptake values [SUVs]) of 18FDG in osteolytic and osteoblastic metastases were compared. Survival was compared for both lytic and blastic bone metastases and for patients with high and low accumulation of 18FDG. RESULTS: 18FDG PET detected more lesions than 99mTc MDP scintigraphy (mean, 14.1 and 7.8 lesions, respectively; P < .01). However, 18FDG detected fewer bone metastases compared with 99mTc MDP scintigraphy in a subgroup of patients with osteoblastic disease (P < .05). Higher SUVs were observed for osteolytic than osteoblastic disease (mean, 6.77 and 0.95, respectively; P < .01). Survival was lower in patients with osteolytic disease compared with the remainder (P=.01). A difference in survival was not found for those patients with high SUVs (> 3.6; P=.4). CONCLUSION: 18FDG PET is superior to bone scintigraphy in the detection of osteolytic breast cancer metastases, which led to a poorer prognosis. In contrast, osteoblastic metastases show lower metabolic activity and are frequently undetectable by PET. The biologic explanation for this observation remains to be elucidated.     

Phylloid pigmentary pattern with mosaic trisomy 13

PET is a diagnostic method that creates high resolution, 3 dimensional tomographic images of the distribution of positron emitting radionuclides in the human body. Recent technological developments allow the use of whole-body PET devices in clinical oncology. 18FDG is a glucose analog transported and competitively used with glucose reflecting the increased glucose metabolism into malignant cells. Differential diagnosis between chronic pancreatitis and pancreatic cancer is already a well-documented indication. For initial staging of gastro-esophageal and colorectal tumours, results are preliminary but the clinical impact seems to be rather limited. At present, the major indication of FDG-PET is the detection and staging of colorectal cancer recurrences. FDG-PET allows the differentiation between scared tissue and tumour when structural imaging is often confusing. In the same time, the whole-body imaging capability provides unique information that can modify loco-regional and liver staging. Overall, FDG-PET affects the clinical management of 30 to 40% of these patients. Quantitative assessment of therapeutic response to chemotherapy regimen appears to be one of the most promising applications of FDG-PET. Since the most effective therapy of colorectal cancer are often surgical, the role of chemotherapy in colorectal cancer remains limited to adjuvant therapy and in advanced disease. However, FDG-PET could be of great value in assessing the response of oesophageal carcinomas to chemo-radio therapy, before surgery. In our experience, FDG-PET appears to be the first line diagnostic method in the detection and staging of colorectal recurrence and differential diagnosis of pancreatic tumour versus chronic pancreatitis.     

Can dual-headed 18F-FDG SPET imaging reliably supersede PET in clinical oncology? A comparative study in lung and gastrointestinal tract cancer

In this study, we prospectively compared the sensitivity of PET and planar SPET (collimated gamma camera) 18F-FDG imaging in patients with lung and gastrointestinal tract cancer and analysed their respective impact on patient management. Twenty-eight patients with lung cancer and 14 with gastro-intestinal tract tumours were scanned on the same day with a PET and a collimated planar SPET gamma camera. The planar SPET procedure consisted of whole-body planar views and a tomographic acquisition centred over the torso or the abdomen, with the total imaging time within the same range as the whole-body PET procedure. The staging of lung cancer patients was accurate in 86% with PET and 64% with planar SPET. Planar SPET would have led to inappropriate therapeutic decisions in 8 of 28 patients, mainly due to undetected distant metastases. In patients with suspected gastrointestinal tract cancer, planar SPET identified 7 of 15 (47%) proven tumour sites, whereas PET identified 14 of 15 (93%). Our results suggest that collimated planar SPET cameras are not a substitute for dedicated PET scanners. The sensitivity for the detection of tumours is unacceptably low and can impair patient management. The use of multiple tomographic acquisitions could improve the sensitivity but would require a longer scanning time.     

Applications of PET in lung cancer

An estimated 180,000 new cases of lung cancer will be diagnosed in the United States this year, and lung cancer accounts for approximately 25% of all cancer deaths. The overall 5-year survival rate is 14%, and this has not changed over the past several decades. Lung cancer diagnosis and treatment is a major health problem globally. Most lung cancers are detected initially on chest radiographs, but many benign lesions have radiologic characteristics similar to malignant lesions. Thus, additional studies are required for further evaluation. Computed tomography (CT) is most frequently used to provide additional anatomic and morphologic information about the lesion, but it is limited in distinguishing benign from malignant abnormalities in the lung, pleura, and mediastinum. Because of the indeterminate results from anatomic imaging, biopsy procedures including thoracoscopy and thoracotomy may be used even through one-half of the lesions removed are benign and do not need to be removed. FDG-PET imaging provides physiologic and metabolic information that characterizes lesions that are indeterminate by CT and that accurately stages the distribution of lung cancer. Exploiting the fundamental biochemical differences between cancer and normal tissues, FDG imaging takes advantage of the increased accumulation of FDG in transformed cells. FDG-PET is very sensitive (approximately 95%) for the detection of cancer in patients who have indeterminate lesions on CT. The specificity (approximately 85%) of PET imaging is slightly less than the sensitivity because some inflammatory processes such as active granulomatous infections accumulate FDG avidly. The high-negative predictive value of PET suggests that lesions considered negative on the study are benign, biopsy is not needed, and radiographic follow-up is recommended. Several studies have documented the increased accuracy of PET compared with CT in the evaluation of the hilar and mediastinal lymph node status in patients with lung cancer. If the mediastinum is normal on PET imaging and there is no other evidence of metastatic disease, the patient has a thoracotomy. If the mediastinum is abnormal on PET imaging, mediastinoscopy is performed with the PET images providing the lymph node stations to target. Whole-body PET studies detect metastatic disease that is unsuspected by conventional imaging and demonstrate some of the anatomic abnormalities detected by CT to be benign lesions. Management changes have been reported to occur in up to 41% of patients based on the results of the whole-body studies.     

In-111 monoclonal antibody versus Ga-67 citrate and Tc-99m SC subtraction in a patient with malignant melanoma

Gallium-67 is routinely used for follow-up of patients with malignant melanoma. However, its nonspecificity for melanoma and its high rate of false-positive results have always been a matter of concern. The authors describe a patient who encountered serious problems with the use of gallium. Because gallium is taken up well by the liver and by melanoma, results of gallium scintigraphy of the liver may appear normal even if there is metastatic disease. In this patient, results of gallium scintigraphy of the liver were negative for metastasis but revealed extrahepatic foci detected by the monoclonal antibody. Computed tomography showed areas of attenuation, revealing only a few intrahepatic tumors and no extrahepatic disease. Tc-99m SC revealed intrahepatic metastases, but no extra-hepatic metastases were seen. A monoclonal antibody (ZME-018) scintigram did reveal hepatic metastases along with probable small, extrahepatic, metastatic foci. Overall hepatic uptake of the monoclonal antibody was relatively low. An image subtraction algorithm was devised whereby the sulfur colloid image was subtracted from the gallium scintigram. The resultant image revealed both the intrahepatic and extrahepatic metastases seen on the ZME-018 images. It is likely that in the past many hepatic metastases have been missed because Tc-99m SC images have not been routinely used as part of melanoma management protocols. The uptake of the ZME-018 by the tumor was significantly higher than that of the normal liver, suggesting that ZME-018 labeled with the appropriate emitter may be an effective specific therapeutic tool in selected patients.