¹8F-FDG-PET imaging in radiotherapy tumor volume delineation in treatment of head and neck cancer.

PURPOSE: To determine the impact of (18)F-fluorodeoxyglucose positron emission tomography (PET) in radiotherapy target delineation and patient management for head and neck squamous cell carcinoma (HNSCC) compared to computed tomography (CT) alone. MATERIALS AND METHODS: Twenty-nine patients with HNSCC were included. CT and PET/CT obtained for treatment planning purposes were reviewed respectively by a neuroradiologist and a nuclear medicine specialist who were blinded to the findings from each other. The attending radiation oncologist together with the neuroradiologist initially defined all gross tumor volume of the primary (GTVp) and the suspicious lymph nodes (GTVn) on CT. Subsequently, the same radiation oncologist and the nuclear medicine specialist defined the GTVp and GTVn on (18)F-FDG-PET/CT. Upon disagreement between CT and (18)F-FDG-PET on the status of a particular lymph node, an ultrasound-guided fine needle aspiration was performed. Volumes based on CT and (18)F-FDG-PET were compared with a paired Student's t-test. RESULTS: For the primary disease, four patients had previous diagnostic tonsillectomy and therefore, FDG uptake occurred in 25 patients. For these patients, GTVp contoured on (18)F-FDG-PET (GTVp-PET) were smaller than the GTVp contoured on CT (GTVp-CT) in 80% of the cases, leading to a statistically significant volume difference (p=0.001). Of the 60 lymph nodes suspicious on PET, 55 were also detected on CT. No volume change was observed (p=0.08). Ten biopsies were performed for lymph nodes that were discordant between modalities and all were of benign histology. Distant metastases were found in two patients and one had a newly diagnosed lung adenocarcinoma. CONCLUSIONS: GTVp-CT was significantly larger when compared to GTVp-PET. No such change was observed for the lymph nodes. (18)F-FDG-PET modified treatment management in three patients, including two for which no curative radiotherapy was attempted. Larger multicenter studies are needed to ascertain whether combined (18)F-FDG-PET/CT in target delineation can influence the main clinical outcomes.

Impact of intravenous insulin on 18F-FDG PET in diabetic cancer patients.

UNLABELLED: The aims of this study were to evaluate the effectiveness of a standardized insulin protocol in reducing glycemia, review (18)F-FDG biodistribution with such a protocol, and assess its clinical impact. METHODS: Sixty-three patients with glycemia greater than 10 mmol/L received insulin doses intravenously according to a standardized protocol. One hundred six consecutive euglycemic patients (<6.2 mmol/L) served as controls. (18)F-FDG biodistribution was evaluated by 2 experienced PET readers on a 5-point visual scale based on muscular uptake. The 63 patients who received insulin were divided into insulin subgroup A, with adequate biodistribution (score 0, 1, or 2) and insulin subgroup B, with altered biodistribution (score 3 or 4). 18F-FDG biodistribution was also evaluated semiquantitatively by standardized uptake value (SUV) measurements over the liver, gluteal muscles, and myocardium. Clinical impact (complications and diagnostic accuracy) was assessed by follow-up. RESULTS: Glycemia decreased from 13+/-2 to 7+/-2 mmol/L after insulin injection. Images showed significantly more muscular uptake in patients who received insulin than in the control group (scores 1.6+/-1.5 vs. 0.4+/-0.6, P<0.05). Twenty-five percent of insulin patients studied had altered biodistribution (insulin subgroup B). The two most important factors increasing muscular uptake were the time interval between insulin and 18F-FDG injection (mean in insulin subgroup A, 80.2+/-17 min; mean in insulin subgroup B, 65.7+/-10 min; P<0.01) and the glycemia interval decrease after insulin injection (mean in insulin subgroup A, 5.3+/-2.6 mmol/L; mean in insulin subgroup B, 7.6+/-1.8 mmol/L; P<0.01). In insulin subgroup B, mean hepatic SUV was lower (1.3+/-0.4 vs. 2.1+/-0.4, P<0.01) and mean muscular SUV was higher (1.8+/-0.1 vs. 0.9+/-0.01, P<0.01). Of the 63 patients who received insulin, 6 had hypoglycemia, but only 2 were symptomatic. No patient had severe complications causing permanent disability. CONCLUSION: A standardized protocol of intravenous insulin before 18F-FDG injection in diabetic cancer patients was safe and effective in reducing glycemia. Acceptable 18F-FDG biodistribution was obtained in 75% of patients receiving insulin. In addition to visually increased muscular uptake, low hepatic 18F-FDG uptake was a good indicator of altered biodistribution.

Chilaiditi sign on FDG-PET.

A 66-year-old woman with a history of endometrial cancer underwent a F-18 fluorodeoxyglucose positron emission tomography (FDG-PET). Abnormal uptake was noted in the right lower chest. CT scan showed a loop of colon interposed between the liver and the diaphragm, an entity known as the Chilaiditi sign. This case illustrates the importance to correlate abnormal PET findings with CT images. The Chilaiditi sign should be included in the differential diagnosis of lower chest uptake on an FDG-PET study.

Bone marrow hypermetabolism on 18F-FDG PET as a survival prognostic factor in non-small cell lung cancer.

UNLABELLED: PET is now widely used in the diagnosis and staging of lung cancer with (18)F-FDG. The purpose of the study was to evaluate the prognostic value of diffuse bone marrow hypermetabolism along with other PET prognostic factors with respect to survival and compare them with other established prognostic factors in a large cohort of patients. METHODS: Of 255 patients referred for evaluation of a suspicious lung lesion by PET over an 8-mo period (May 1999 to January 2000), the outcome of 120 patients with a final diagnosis of primary non-small cell lung cancer was analyzed retrospectively after excluding subjects with benign, metastatic, or recurrent lesions, using the available follow-up information and a provincial mortality database. Kaplan-Meier survival curves were compared using the mean and the maximal tumor standardized uptake value (SUV), bone marrow SUV, PET stage, various laboratory parameters, sex, age, conventional imaging stage, and pathologic stage. A stepwise Cox proportional hazard model was built using the significant variables on univariate analysis. RESULTS: The primary tumor SUV (>10), bone marrow uptake of (18)F-FDG, (18)F-FDG PET stage, pathologic stage, hypercalcemia, lactate dehydrogenase, hemoglobin, albumin, thrombocytopenia, thrombocytosis, and leukocytosis were predictors of mortality on univariate analysis. On multivariate analysis, bone marrow hypermetabolism, (18)F-FDG PET nodal stage, and some hematologic parameters (hemoglobin, platelets, white blood cell counts) remained significant independent predictors of mortality. CONCLUSION: Bone marrow hypermetabolism and the PET nodal stage were strong independent predictors of mortality in patients with lung cancer. The primary tumor SUV, though predictive on univariate analysis, was not an independent predictor of mortality in our model.

Respiratory gating for 3-dimensional PET of the thorax: feasibility and initial results.

UNLABELLED: Respiratory motion may reduce the sensitivity of (18)F-FDG PET for the detection of small pulmonary nodules close to the base of the lungs. This motion also interferes with attempts to use fused PET/CT images through software or combined PET/CT devices. This study was undertaken to assess the feasibility of respiratory gating for PET of the chest and the impact of respiratory motion on quantitative analysis. METHODS: Ten healthy subjects were enrolled in this study. Three-dimensional studies were acquired with 8 gates per respiratory cycle on a commercial PET scanner with a temperature-sensitive respiratory gating device built in-house. All scans were obtained over 42 cm of body length with 3 bed positions of 10 min each after injection of (18)F-FDG at 4.5 MBq/kg. The reconstructed images were assembled to produce gated whole-body volumes and maximum-intensity projections. The amplitude of respiratory motion of the kidneys (as a surrogate for diaphragmatic incursion) as well as the apex of the heart was measured in the coronal plane. Phantom studies were acquired to simulate the impact of respiratory motion on quantitative uptake measurements. RESULTS: The respiratory gating device produced a consistent, reliable trigger signal. All acquisitions were successful and produced reconstructed volumes with excellent image quality. Mean +/- SD motion amplitude and maximal motion amplitude values were 6.7 +/- 3.0 and 11.9 mm for the heart, 12.0 +/- 3.7 and 18.8 mm for the right kidney, and 11.1 +/- 4.8 and 17.1 mm for the left kidney, respectively. In phantom studies, the standardized uptake value for a 1-mL lesion was underestimated by 30% and 48% for the average and maximal respiratory motion values, respectively. CONCLUSION: Respiratory gating of PET of the thorax and upper abdomen is a practical and feasible approach that may improve the detection of small pulmonary nodules. Further work is planned to assess prospectively the diagnostic accuracy of this new method.