Role of 11-C-methionine positron emission tomography for the delineation of the tumor volume in pharyngo-laryngeal squamous cell carcinoma: comparison with FDG-PET and CT.

BACKGROUND AND PURPOSE: Although computed tomography (CT) remains the imaging modality of reference in head and neck squamous cell carcinoma (HNSCC) for the three-dimensional (3D) conformal radiotherapy, its poor soft tissue contrast can hamper precisely delineate the tumor volume. Besides anatomical imaging, 2-[18F] fluoro-2-deoxy-d-glucose-positron emission tomography (FDG-PET) has been shown to enhance the accuracy of the tumor delineation but l-methyl [11C]-methionine-positron emission tomography (MET-PET) has never been tested for this purpose. This study was undertaken to determine the potential added value of MET-PET for the delineation of gross target volume (GTV) in HNSCC, as compared to CT and FDG-PET. PATIENTS AND METHODS: Twenty-three patients (10 oropharynx, 8 larynx and 5 hypopharynx) presenting with stage II-IV HNSCC were prospectively enrolled. They were treated by primary radiotherapy or by total laryngectomy. Images (CT, FDG-PET and MET-PET) were acquired with a thermoplastic mask and after coregistration, tumor volumes were delineated on CT and using an adaptative threshold-based automatic method on FDG- and MET-PET. Absolute volumes as well as the mismatch between modalities were compared. RESULTS: For oropharyngeal lesions, FDG volumes were significantly smaller (19.43 ml+/-21.36) than CT (29.04 ml+/-30.97) (P=0.013). On the other hand, MET volumes (24.36 ml+/-20.59) were not different from CT volumes. Similar results were found for laryngeal and hypopharyngeal tumors, with volume of 24.93 ml+/-19.02 for CT, 21.84 ml+/-15.32 for MET-PET and 14.49 ml+/-11.3 for FDG-PET (P=0.003). Large mismatches were observed between modalities, in particular between CT and PET. CONCLUSIONS: Our study confirms that the use of FDG-PET may result in a significant reduction of GTV's as compared to CT. On the contrary, MET-PET does not have any additional value since MET volumes are not different from CT volumes, probably because of the high uptake of MET by the normal mucosa and salivary glands surrounding the tumor.     

Metabolic characterization of childhood brain tumors: comparison of 18F-fluorodeoxyglucose and 11C-methionine positron emission tomography

BACKGROUND: Positron emission tomography (PET) scans of primary brain tumors were performed in pediatric patients to examine whether metabolic characteristics could be used as an index of clinical aggressiveness. METHODS: Twenty-seven pediatric patients with untreated primary central nervous system neoplasms were studied with PET scans using 2-[(18)F] fluoro-2-deoxy-D-glucose (FDG) and/or L-[methyl-(11)C] methionine (MET). Metabolic characteristics as assessed with FDG and MET standardized uptake values (SUV) and SUV-to-normal brain ratios were compared with histopathology and selected histochemical features such as proliferation activity (Ki-67(MIB-1)) and apoptotic, vascular, and cell density indices. The median followup time was 43 months. RESULTS: The accumulation of both FDG and MET was significantly higher in high-grade than in low-grade tumors, but a considerable overlap was found. The accumulation of both tracers was associated positively with age. High-grade tumors showed higher proliferative activity and vascularity than the low-grade tumors. In univariate analysis, FDG-PET, MET-PET, and apoptotic index were independent predictors of event-free survival. CONCLUSION: We found that both FDG and MET uptake in pediatric brain tumors are associated with malignancy grade. However, no clear limits of SUVs and SUV-to-normal brain ratios can be set between low-grade and high-grade tumors, which makes the assessment of malignancy grade using metabolic imaging with PET scan difficult in individual cases. Although FDG-PET and MET-PET do not compensate for histopathologic evaluation, they may give valuable additional information especially if invasive procedures to obtain histopathologic samples are not feasible.     

L-(methyl-11C) methionine positron emission tomography for target delineation in resected high-grade gliomas before radiotherapy

PURPOSE: Using magnetic resonance imaging (MRI), residual tumor cannot be differentiated from nonspecific postoperative changes in operated patients with brain gliomas. The higher specificity and sensitivity of L-(methyl-11C)-labeled methionine positron emissions tomography (MET-PET) in gliomas has been demonstrated in previous studies and is the rationale for the integration of this investigation in gross tumor volume delineation. The goal of this trial was to quantify the affect of MET-PET vs. with MRI in gross tumor volume definition for radiotherapy planning of high-grade gliomas. METHODS AND MATERIALS: The trial included 39 patients with resected malignant gliomas. MRI and MET-PET data were coregistered based on mutual information. The residual tumor volume on MET-PET and the volume of tissue abnormalities on T1-weighted MRI (gadolinium [Gd] enhancement) and T2-weighted MRI (hyperintensity areas) were compared using MET-PET/MRI fusion images. RESULTS: The MET-PET vs. Gd-enhanced T1-weighted MRI analysis was performed on 39 patients. In 5 patients (13%), MET uptake corresponded exactly with Gd enhancement, and in 29 (74%) of 39 patients, the region of MET uptake was larger than that of the Gd enhancement. In 27 (69%) of the 39 patients, the Gd enhancement area extended beyond the MET enhancement. MET uptake was detected up to 45 mm beyond the Gd enhancement. MET-PET vs. T2-weighted MRI was investigated in 18 patients. MET uptake did not correspond exactly with the hyperintensity areas on T2-weighted MRI in any patient. In 9 (50%) of 18 patients, MET uptake extended beyond the hyperintensity area on the T2-weighted MRI, and in 18 (100%), at least some hyperintensity on the T2-weighted MRI was located outside the MET enhancement area. MET uptake was detected up to 40 mm beyond the hyperintensity area on T2-weighted MRI. CONCLUSION: In operated patients with brain gliomas, the size and location of residual MET uptake differs considerably from abnormalities found on postoperative MRI. Because postoperative changes cannot be differentiated from residual tumor by MRI, MET-PET, with a greater specificity for tumor tissue, can help to outline the gross tumor volume with greater accuracy.     

The value of F-18-fluorodeoxyglucose PET for the 3-D radiation treatment planning of malignant gliomas

Purpose: The aim of the study was to determine the impact of positron emission tomography using the glucose analogue fluorine-18-fluorodeoxyglucose (FDG-PET) on the delineation of the target volume in three-dimensional radiation treatment planning of primary brain tumors.

Methods and Materials: In 18 patients with histologically proven (8× biopsy, 10× subtotal resection) primary brain tumors (8 astrocytomas °III, one mixed glioma °III, and 9 glioblastomas), magnetic resonance imaging (MRI) with gadolinium-DTPA and FDG-PET were performed in radiation treatment position within the same week. A computer program was developed for fusion of the PET and MR images. On corresponding axial slices, FDG uptake was compared to contrast enhancement in T1-weighted and to signal hyperintensity in T2-weighted MR images. Based on PET and MRI data, three-dimensional treatment planning was performed. All patients underwent linear accelerator (LINAC) radiotherapy.

Results: In MRI, all tumors and the surrounding edema were visible as hyperintense lesions in the T2-weighted images. 17/18 tumors showed contrast enhancement. In FDG-PET, 16 tumors showed hypermetabolism compared to normal white matter, whereas only 8/18 tumors showed hypermetabolism compared to normal gray matter. White matter edema was associated with decreased FDG uptake in all patients. The area of increased FDG uptake correlated closely with contrast enhancement, only in one case the volume of increased FDG uptake was larger than the area of contrast enhancement. Mean tumor volumes obtained by MRI T1 + Gd, T2, and PET were 30, 106, and 10 ml, respectively. Survival was comparable to data in the literature with a 1-year survival of 39% and a median survival of 310 days.

Conclusion: Only in a minority of patients did FDG-PET provide additional information for radiation treatment planning. This is mainly caused by the high intensity of FDG uptake in normal brain tissue. PET may be of greater value in the definition of regions that should obtain a radiation dose boost.     

Detection of histological anaplasia in gliomas with oligodendroglial components using positron emission tomography with 18F-FDG and 11C-methionine: report of two cases

Gliomas are regionally heterogeneous tumors. Positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (FDG) and ¹¹C-methionine (MET) evaluates the heterogeneity of histological malignancy within the tumor. We present two patients with oligodendrocytic tumors that showed discrepancies in the highest uptake areas with these two tracers. PET studies with MET and FDG were performed on the same day, 2 weeks before surgery. In both cases, biopsy specimens were separately obtained from the highest MET and FDG uptake areas guided by intraoperative neuronavigation. Histological examinations demonstrated that the specimens from the highest MET uptake area revealed low-grade oligoastrocytoma or oligodendroglioma, whereas histological anaplasias were contained in the specimens from the highest FDG uptake area. With gliomas with oligodendroglial components, the MET uptake ratio does not always correspond to histological anaplasia, which can be detected only by FDG PET. Sole application of MET PET for preoperative evaluation may lead to misunderstanding of histological heterogeneity in gliomas, especially those with oligodendroglial components. FDG and MET tracers play complementary roles in preoperative evaluation of gliomas.     

Delineation of brain tumor extent with [11C]L-methionine positron emission tomography: local comparison with stereotactic histopathology.

PURPOSE: Methyl-[11C]L-methionine ([11C]MET) positron emission tomography (PET) in brain tumors reflects amino acid transport and has been shown to be more sensitive than magnetic resonance imaging in stereotactic biopsy planning. It remains unclear whether the increased [11C]MET uptake is limited to solid tumor tissue or even detects infiltrating tumor parts. EXPERIMENTAL DESIGN: In 30 patients, a primary or recurrent brain tumor was suspected on magnetic resonance imaging. Patients were investigated with [11C]MET-PET before stereotactic biopsy. The biopsy trajectories were plotted into the [11C]MET-PET images with a newly designed C-based software program. The exact local [11C]MET uptake was determined within rectangular regions of interest of 4 mm in width and length aligned with the biopsy specimen. Individual histologic specimens were rated for the presence of solid tumor tissue, infiltration area, and nontumorous tissue changes. RESULTS: Receiver operating characteristics analysis demonstrated a sensitivity of 87% and specificity of 89% for the detection of tumor tissue at a threshold of 1.3-fold [11C]MET uptake relative to normal brain tissue. At this threshold, only 13 of 100 tumor positive specimen were false negative mainly in grade 2 astrocytoma. In grade 2 astrocytoma, mean [11C]MET uptake in the infiltration area was significantly higher than in solid tumor tissue (P < 0.003). CONCLUSIONS: [11C]MET-PET detects solid parts of brain tumors, as well as the infiltration area at high sensitivity and specificity. High [11C]MET uptake in infiltrating tumor of astrocytoma WHO grade 2 reflects high activity in this tumor compartment. Molecular imaging, with [11C]MET, will guide improved management of patients with brain tumors.     

Contributions of biological tumor parameters to the incorporation rate of <Emphasis Type="SmallCaps">l</Emphasis>-[methyl-<Superscript>11</Superscript>C] methionine into astrocytomas and oligodendrogliomas

We compared the tumor uptake of ¹¹C-methionine (MET) with positron emission tomography (PET) with the results of a pathological analysis to examine the proliferative potential and microvessel density measured with immunostaining for MIB-1 and factor VIII, respectively, from 33 patients with glioma. The MET uptake in oligodendrogliomas was significantly greater than that in grade 2 astrocytomas and comparable to those in grade 3 and 4 astrocytomas. The MIB-1 index of oligodendroglioma meanwhile was comparable to that of grade 2 astrocytoma. The microvessel area in oligodendroglioma was significantly greater than that in grade 2 astrocytomas and comparable to those in grade 3 and 4 astrocytomas. According to a multivariate statistical analysis, MET uptake ratio was closely correlated with the MIB-1 index among astrocytomas. An increase in the microvessel area in the oligodendrogliomas contributed to the higher MET uptake among the tumors with a low-proliferative index. This information is important for interpreting the results of MET-PET studies for clinical use.     

Simultaneous integrated boost technique by helical tomotherapy for the treatment of glioblastoma multiforme with 11C-methionine PET: report of three cases

We performed hypofractionated high-dose irradiation of a patient’s residual glioblastoma multiforme using a simultaneous integrated boost (SIB) technique with helical tomotherapy system (HT) planning. The gross tumor volume (GTV)-1 was defined as the area of intensive ¹¹C-methionine (MET) uptake and GTV-2 was defined as the area of moderate MET uptake. The planning target volume (PTV)-1 encompassed GTV-1 plus a 5 mm margin, and PTV-2 encompassed GTV-2 plus a 2 mm margin. SIB with HT was performed in eight fractions, planning the dose for GTV-1 at 68 Gy (biologically effective dose: BED = 126 Gy), PTV-1 at 56 Gy (BED = 95 Gy), and PTV-2 at 40 Gy (BED = 60 Gy). In each of the target areas, the uptake value on ¹¹C-methionine positron emission tomography (MET-PET) was considerably decreased following SIB, although no remarkable changes were demonstrated on magnetic resonance imaging (MRI). These cases demonstrate that SIB with HT planning using MET-PET offers excellent target coverage and uniformity. In addition, SIB with HT planning using MET-PET is organ sparing and MET-PET has great efficacy for monitoring treatment response after SIB. To more clearly define the impact of SIB with HT planning using MET-PET, further investigations are required.     

l-[METHYL-(11)C] methionine positron emission tomography for target delineation in malignant gliomas: impact on results of carbon ion radiotherapy

PURPOSE: To assess the importance of (11)C-methionine (MET)-positron emission tomography (PET) for clinical target volume (CTV) delineation. METHODS AND MATERIALS: This retrospective study analyzed 16 patients with malignant glioma (4 patients, anaplastic astrocytoma; 12 patients, glioblastoma multiforme) treated with surgery and carbon ion radiotherapy from April 2002 to Nov 2005. The MET-PET target volume was compared with gross tumor volume and CTV, defined by using computed tomography/magnetic resonance imaging (MRI). Correlations with treatment results were evaluated between positive and negative extended volumes (EVs) of the MET-PET target for CTV. RESULTS: Mean volumes of the MET-PET targets, CTV1 (defined by means of high-intensity volume on T2-weighted MRI), and CTV2 (defined by means of contrast-enhancement volume on T1-weighted MRI) were 6.35, 264.7, and 117.7 cm(3), respectively. Mean EVs of MET-PET targets for CTV1 and CTV2 were 0.6 and 2.2 cm(3), respectively. The MET-PET target volumes were included in CTV1 and CTV2 in 13 (81.3%) and 11 patients (68.8%), respectively. Patients with a negative EV for CTV1 had significantly greater survival rate (p = 0.0069), regional control (p = 0.0047), and distant control time (p = 0.0267) than those with a positive EV. Distant control time also was better in patients with a negative EV for CTV2 than those with a positive EV (p = 0.0401). CONCLUSIONS: For patients with malignant gliomas, MET-PET has a possibility to be a predictor of outcome in carbon ion radiotherapy. Direct use of MET-PET fused to planning computed tomography will be useful and yield favorable results for the therapy.     

11C-MET PET和MRI对脑高级别神经胶质瘤术后放疗靶区设定的比较研究

目的 评价碳标记蛋氨酸PET(11C-MET PET)和MRI在脑高级别神经胶质瘤(HGG)术后放疗靶区勾画中的价值.方法 选择初治幕上型HGG术后患者37例,在同一治疗体位分别行MET PET和MRI扫描,比较两者判定肿瘤是否残留的一致性,并利用图像融合技术定量比较METPET的高代谢区(VMET)位置和范围与MEI的强化区(VGd)或T2W异常高信号区(VT2)间差异.结果 MET PET和MRI显像均为阳性者19例,阴性者7例,两者检测肿瘤是否残留的一致性为70.3%.30例MET PET阳性者与MRI行图像融合,VMET部分或全部体积位于VGd和VT2之外者分别为29例和17例,所有VGd和VT2均部分或全部体积位于VMET之外.VMET边界与VGd边界最大距离≥2.0 cm占50%,与VT2边界最大距离≥1.0 cm占33%.结论 MET PET和MRI在判断和确定脑HGG术后肿瘤残留及其位置和范围方面存在差异,将MET PET与MRI融合有利于更准确和合理设定放疗靶区.     

FDG-PET predicts survival in recurrent high-grade gliomas treated with bevacizumab and irinotecan

Prognosis of recurrent high-grade glioma (HGG) is poor, although bevacizumab has been documented in that context. This study aimed to determine the independent prognostic value of fluorodeoxyglucose (FDG)-PET on progression-free survival (PFS) and overall survival (OS) of recurrent HGG after combined treatment with bevacizumab and irinotecan, compared with other documented prognostic variables. Twenty-five adult patients with histologically proven HGG were included at recurrence. Brain FDG-PET imaging was performed within 6 weeks of starting chemotherapy with bevacizumab and irinotecan. Response based on MRI was assessed every 2 months according to revised assessment in Neuro-Oncology (RANO) criteria. Median PFS and OS were 4 months (range, 0.9-10.4 months) and 7.2 months (range, 1.2-41.7 months), respectively. At 6 months, PFS and OS rate were 16.0% and 72.0%. FDG uptake was the most powerful predictor of both PFS and OS, using either univariate or multivariate analysis, among all variables tested: histological grade, Karnofsky performance status, steroid intake, and number of previous treatments. Moreover, FDG uptake was also prognostic of response to bevacizumab-based therapy. This study provides the first evidence that pretreatment FDG-PET can serve as an imaging biomarker in recurrent HGG for predicting survival following anti-angiogenic therapy with bevacizumab.     

Usefulness of FDG-PET for early prediction of the response to gefitinib in non-small cell lung cancer

Increased tumor uptake of (18)F-fluorodeoxyglucose (FDG) measured by positron emission tomography (PET) reflects glucose metabolism and proliferative activity of tumor cells. We conducted a study to assess the usefulness of FDG-PET for early prediction of the response to gefitinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), in advanced non-small cell lung cancer (NSCLC). Five NSCLC patients underwent FDG-PET to evaluate changes in FDG uptake at day 2 and 4 weeks after the initiation of gefitinib therapy compared with FDG-PET prior to therapy. FDG uptake was evaluated as the maximum standardized uptake value (SUVmax) of the target lesions, which were assessable by conventional CT. Based on the CT evaluation, two patients exhibited a partial response (PR), two patients had stable disease (SD) with a minor response, and one patient had progressive disease (PD). In patients with PR and SD, SUVmax decreased by 61+/-18% (standard deviation) and 59+/-12%, respectively, on day 2, and by 26+/-6 and 43+/-10%, respectively, at 4 weeks after the initiation of gefitinib. Two patients with SD had decreased FDG uptake within 2 days of initiation of therapy, and achieved progression-free survival (PFS) of more than 12 months. In contrast, SUVmax increased up to 153+/-21% at 2 days and 232+/-73% at 4 weeks in a patient with PD. The present preliminary study suggests that FDG-PET may be able to predict response to gefitinib in the early stage of therapy in patients with advanced NSCLC and may have a potential prognostic role.     

11C] methionine and [18F] fluorodeoxyglucose PET in the follow-up of glioblastoma multiforme

Background The aim of this study was to evaluate the value of [11C] methionine (MET) and [18F] fluorodeoxyglucose (FDG) PET in the follow-up of glioblastoma multiforme (GBM). Patients and methods After surgical and/or conservative treatment, 28 patients (pts) with GBM underwent FDG and MET PET on average 12.7 months after the diagnosis had been established. Scans were evaluated visually and by calculating the maximal tumor SUV as well as the ratio of tumor vs. contralateral region (RTu). The degree of tracer uptake was compared with survival time, disease duration and MRI findings. Results The mean overall duration of survival was 12.7 months. The patients were divided into two groups: those that survived less than 12 months and those that survived longer than 12 months. Focally increased uptake was revealed by MET PET in 24 patients and by FDG PET in 2 patients. On MRI scans, viable tumor tissue was suspected in 18 patients. No correlations were registered between FDG/MET uptake and survival time or disease duration respectively; Kaplan–Meier calculations were negative in this regard. Similarly, negative results were obtained in subgroups of patients who had undergone microsurgical resection and whose disease was at least of 6 months’ duration, and additionally in a subgroup who had undergone their last treatment longer than 6 months ago. With respect to survival groups, a positive MET PET was associated with a sensitivity of 86% and a specificity of 8%. SUV and RTu values did not differ between patients with positive or negative MRI results. Conclusions In this study FDG PET seems to be of limited value in the work-up of recurrent GBM because of its lower sensitivity than MET PET and the fact that it allows no prediction of the outcome. MET PET visualizes viable tumor tissue without adding any prognostic information and appears to be in no way superior to conventional imaging.     

Biodistribution and imaging of FDG in rats with LS174T carcinoma xenografts and focal Escherichia coli infection

OBJECTIVE: The aim of this study was to compare the dynamic distribution of fluorodeoxyglucose (FDG) in malignant and in infectious lesions. METHODS: The dynamic distribution of FDG was studied in Rowett nude (RNU) rats with a LS174T carcinoma xenograft in the left front leg and an Escherichia coli-induced focal infection in the right front leg. In 5 rats, dynamic FDG-PET was performed (27 frames of 6-15 minutes) up to 4 hours after injection of 11 MBq 18FDG. The mean FDG uptake (SUV) was calculated and plotted by using a region of interest (ROI) centered over both lesions. In groups of 6 rats, the biodistribution of FDG was determined by counting dissected tissues at 1, 2, 3, and 4 hours after an injection of 11 MBq FDG. Means +/- the standard error of the mean (SEM) were calculated. RESULTS: Dynamic positron emission tomography (PET) visualized both the tumor and the infection. The ROI analysis showed that FDG uptake in the infections was faster and higher, as compared to the tumor lesions. FDG uptake in the tumor reached a standardized uptake value (SUV) of 0.8 +/- 0.3 at 60 minutes and in the infectious lesions a SUV of 1.6 +/- 0.2 at 45 minutes, both remaining constant until 4 hours postinjection (p.i.). In the biodistribution study with ex vivo tissue counting, FDG had accumulated up to 1.1 +/- 0.1 %ID/g and 0.8 +/- 0.1 %ID/g at 1 hour in the tumor and infection, respectively, and remained constant until 4 hours for both lesions without significantly different wash-out from the 2 lesions. The tumor/blood and abscess/ blood ratios increased with time to 57 +/- 17 and 48 +/- 14, respectively. CONCLUSION: Although in this model differences in absolute FDG uptake and initial kinetics between tumor and infection were observed, the wash-out rate of FDG from the lesions was similar over time. The retention of FDG in the inflammatory lesion indicated that dual time-point imaging does not necessarily resolve diagnostic pitfalls for FDG-PET in oncology in order to discriminate between malignant tumorous and benign infectious lesions.     

Positron Emission Tomography with 18-Fluorodeoxyglucose in the Staging and Follow-up of Lymphoma in the Chest

The purpose of this retrospective study was to evaluate the accuracy of positron emission tomography (PET) using 18-F-fluorodeoxyglucose (FDG) in predicting lymphomatous involvement in the hilar and mediastinal regions in the staging and follow-up of patients with malignant lymphoma. One hundred forty-seven thoracic PET studies in 89 consecutive lymphoma patients were reviewed. Static FDG-PET imaging was performed following application of 270 MBq FDG (mean). Results of FDG-PET were compared with the findings of computed tomography (CT) in all patients and clinical follow-up examination. Eighty-nine of 147 (60%) PET studies showed no FDG uptake in the hilar or mediastinal regions, while 58 (40%) studies did detect FDG uptake in these regions. In 52 of 58 abnormal studies (90%), lymphomatous involvement of the hilar and/or mediastinal regions seen by CT was present. In the remaining six abnormal PET studies (10%), FDG uptake was considered as false-positive because of missing lesions on corresponding CT scans. In four patients false-positive FDG uptake was observed before treatment, in two patients after completion of therapy. In these two patients FDG uptake after therapy was caused by thymus hyperplasia. The remaining four cases before treatment remained unresolved. Sensitivity of FDG-PET was 96%, specificity 94%, positive predictive value 90%, and negative predictive value 98%, respectively. The present study suggests that FDG-PET has potential value in predicting lymphomatous involvement in the hilar and mediastinal regions. FDG-PET may obviate invasive diagnostic procedures in patients with lymphoma.     

Radiotherapy treatment planning and long-term follow-up with [(11)C]methionine PET in patients with low-grade astrocytoma

PURPOSE: To evaluate the feasibility of [(11)C]-methionine positron emission tomography (MET PET) in radiotherapy (RT) treatment planning and long-term follow-up in patients with low-grade glioma. PATIENTS: Thirteen patients with low-grade astrocytoma and 1 with anaplastic astrocytoma underwent sequential MET PET and magnetic resonance imaging (MRI) before and 3, 6, 12, and 21-39 months after RT, respectively. Ten patients were studied after initial debulking surgery or biopsy and 4 in the recurrence phase. METHODS: A total of 58 PET scans were performed. After transmission scanning, a median dose of 425 MBq of MET was injected intravenously and emission data was acquired 20 min after injection for 20 min. The uptake of MET in tumor area was measured as standardized uptake value (SUV) and tumor-to-contralateral brain SUV ratios were generated to assess irradiation effects on tumor metabolism. Functional imaging with PET was compared with concurrent MRI in designing the RT planning volumes and in assessment of response to RT during a median follow-up time of 33 months. RESULTS: In 12 patients (86%), tumor area was clearly discernible in the baseline PET study. In the remaining 2 patients with a suspected residual tumor in MRI, PET showed only a diffuse uptake of MET interpreted as negative in the original tumor area. In the dose planning of RT, MET PET was helpful in outlining the gross tumor volume in 3 of 11 cases (27%), whereas PET findings either coincided with MRI (46%) or were less distinctive (27%) in other cases. In quantitative evaluation, patients with a low tumor SUV initially had significantly better prognosis than those with a high SUV. Tumor-to-contralateral brain uptake ratios of MET discriminated well patients remaining clinically stable from those who have since relapsed or died of disease. CONCLUSION: Quantitative MET PET has prognostic value at the time of initial treatment planning of low-grade glioma. Some patients may benefit of RT volume definition with MET PET, which seems to disclose residual tumor better than MRI in selected cases. Stable or decreasing uptake of MET in tumor area after RT during follow-up seems to be a favorable sign.     

Repeat 18F-FDG PET for monitoring neoadjuvant chemotherapy in patients with stage III non-small cell lung cancer

PURPOSE: The relevance of (18)F-FDG PET for staging non-small cell lung cancer (NSCLC), in particular for the detection of lymph node or distant metastases, has been shown in several studies. The value of FDG-PET for therapy monitoring in NSCLC, in contrast, has not yet been sufficiently analysed. Aim of this study was to evaluate FDG-PET for monitoring treatment response during and after neoadjuvant radiochemotherapy (NARCT) in advanced NSCLC. METHODS: Sixty-five patients with histologically proven NSCLC stage III initially underwent three FDG-PET investigations, during NARCT prior to initiating radiation, and post-NARCT. Changes of FDG-uptake in the primary tumour at two time-points during NARCT were analysed concerning their impact on long-term survival. RESULTS: The mean maximum FDG uptake (standardized uptake value, SUVmax) of the whole group decreased significantly during NARCT (SUVmax PET 1: 14.9+/-4.0, SUVmax PET 3: 5.5+/-2.4, p=0.004). The difference between initial FDG uptake (PET 1) and uptake after induction chemotherapy (PET 2) was found to be highly predictive for long-term survival patients which had a greater than 60% decreases in their SUV change had a significantly longer survival than those below this threshold (5-year-survival 60% versus 15%, p=0.0007). Patients who had a lower than 25% decrease in their SUV change had a 5-years-survival lower than 5%. Furthermore, the difference between initial FDG uptake (PET 1) and uptake after completion of the whole NARCT (PET 3) was predictive for survival when 75% was applied as cut-off (p=0.02). However, the level of significance was considerably lower. CONCLUSION: FDG-PET is suitable for therapy monitoring in patients with stage III NSCLC. The decrease of FDG uptake during induction chemotherapy is highly predictive for patient outcome.     

Accuracy of distinguishing between dysembryoplastic neuroepithelial tumors and other epileptogenic brain neoplasms with [11C]methionine PET

Background

Dysembryoplastic neuroepithelial tumors (DNTs) represent a prevalent cause of epileptogenic brain tumors, the natural evolution of which is much more benign than that of most gliomas. Previous studies have suggested that [¹¹C]methionine positron emission tomography (MET-PET) could help to distinguish DNTs from other epileptogenic brain tumors, and hence optimize the management of patients. Here, we reassessed the diagnostic accuracy of MET-PET for the differentiation between DNT and other epileptogenic brain neoplasms in a larger population.

Methods

We conducted a retrospective study of 77 patients with focal epilepsy related to a nonrapidly progressing brain tumor on MRI who underwent MET-PET, including 52 with a definite histopathology. MET-PET data were assessed by a structured visual analysis that distinguished normal, moderately abnormal, and markedly abnormal tumor methionine uptake and by semiquantitative ratio measurements.

Results

Pathology showed 21 DNTs (40%), 10 gangliogliomas (19%), 19 low-grade gliomas (37%), and 2 high-grade gliomas (4%). MET-PET visual findings significantly differed among the various tumor types (P < .001), as confirmed by semiquantitative analyses (P < .001 for all calculated ratios), regardless of gadolinium enhancement on MRI. All gliomas and gangliogliomas were associated with moderately or markedly increased tumor methionine uptake, whereas 9/21 DNTs had normal methionine uptake. Receiver operating characteristics analysis of the semiquantitative ratios showed an optimal cutoff threshold that distinguished DNTs from other tumor types with 90% specificity and 89% sensitivity.

Conclusions

Normal MET-PET findings in patients with an epileptogenic nonrapidly progressing brain tumor are highly suggestive of DNT, whereas a markedly increased tumor methionine uptake makes this diagnosis unlikely.     

The Clinical Significance of Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography in Patients with Occupational Cholangiocarcinoma

Objective: The present study aimed to identify the clinical significance of fluorine-18 fluorodeoxyglucose positronemission tomography (FDG-PET) imaging in patients with occupational cholangiocarcinoma. Methods: This studyincluded 10 men with occupational cholangiocarcinoma who were former or current workers at a printing company inOsaka, Japan. Of the 10 patients, 2 had 2 main tumors and 1 had 3 main tumors. Twelve FDG-PET imaging findingsin the 10 patients could be analyzed. We evaluated the relationships between FDG-PET imaging parameters andclinicopathological findings of occupational cholangiocarcinoma. Results: Abnormal FDG uptake was observed in 8 ofthe 14 main tumors, with maximum standardized uptake values ranging from 2.9 to 11.0, and the sensitivity was 57.1%.Four patients had lymph node metastases, and abnormal marrow uptake was detected in all these patients. Althoughprecancerous lesions, such as biliary intraepithelial neoplasia (BilIN) and intraductal papillary neoplasm of the bileduct (IPNB) without any invasion, were not detected, abnormal FDG uptake was demonstrated in 2 of 4 patients withIPNB having an associated invasive carcinoma.Conclusions: Although FDG-PET may be useful for assessing tumorprogression factors, such as lymph node metastasis, it cannot accurately detect precancerous lesions, such as BilINand IPNB without invasive carcinoma.