Utility of 18F-FDG PET/CT uptake patterns in Waldeyer's ring for differentiating benign from malignant lesions in lateral pharyngeal recess of nasopharynx.

UNLABELLED: Focally increased (18)F-FDG uptake in the lateral pharyngeal recess (LPR) of the nasopharynx due to a benign or malignant lesion is not an uncommon finding on PET images. The aim of this study was to evaluate whether, on PET/CT images, (18)F-FDG uptake occurs with characteristic patterns and intensities in various regions of Waldeyer's ring that can improve our ability to differentiate benign from malignant lesions. METHODS: Data generated from the (18)F-FDG PET/CT images of 1,628 subjects in our cancer-screening program were analyzed. Increased uptake in the LPR was observed in 80 subjects (4.9%) presenting with benign lesions, including 53 subjects without and 27 subjects with symptoms of upper airway discomfort. In addition, 30 healthy controls and 21 patients with newly diagnosed nasopharyngeal carcinoma were recruited for this study. Visual uptake, measurements of the lesions' standardized uptake value (SUV), and any abnormalities on PET/CT were evaluated. The receiver-operating-characteristic curve and area under the curve were applied to evaluate the discriminating power. RESULTS: Increased (18)F-FDG uptake (SUV, mean +/- SD) was found in the LPR, with a statistically significant (P < 0.001) difference between benign lesions (3.0 +/- 1.16) and malignant lesions (7.03 +/- 3.83). However, associated increased uptake exclusively in the palatine tonsil, lingual tonsil, and submandibular gland was found in both asymptomatic and symptomatic subjects. The ratio of LPR uptake to palatine tonsil uptake (N/P ratio) in benign lesions (0.81 +/- 0.37) was significantly (P < 0.001) lower than that in malignant lesions (2.30 +/- 1.62). Higher incidences of asymmetric (18)F-FDG LPR uptake, cervical lymph node uptake, and asymmetric wall thickening of the LPR on CT were observed in patients with nasopharyngeal carcinoma. When an SUV of less than 3.9 and an N/P ratio of less than 1.5 were used as cutoff points in subjects showing the combination of symmetric uptake in the LPR and normal or symmetric wall thickening, and detectable lymph node uptake, the area under the curve for benign lesions on PET/CT was 0.932 +/- 0.042 (95% confidence interval, 0.86-0.98), with a sensitivity of 90.4% and a specificity of 93.8%. CONCLUSION: The intensity and patterns of (18)F-FDG uptake in various regions of Waldeyer's ring along with CT scan findings provide a feasible modality to differentiate benign from malignant nasopharyngeal lesions.

Clinical usefulness of fused PET/CT compared with PET alone or CT alone in nasopharyngeal carcinoma patients.

UNLABELLED: The diagnostic accuracy of fused positron emission tomography/computed tomography (PET/CT) was compared with CT alone and PET alone in the staging and re-staging of nasopharyngeal carcinoma (NPC) patients. PATIENTS AND METHODS: Eighty-six fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG) PET/CT studies were retrospectively performed in 70 patients with NPC, 20 patients for primary tumor staging and 50 patients for re-staging after treatment. Each lesion was analyzed visually and assigned a score on a 5-point scale. Each study was interpreted in 3 ways: PET images were evaluated in the absence of CT data, CT images in the absence of PET data and fused PET/CT images. The results of these images were correlated with histological findings, as well as long-term radiological and clinical follow-up (the shortest follow-up period after imaging was 6 months). PET, CT and PET/CT accuracy were compared by a McNemar test. RESULTS: Fused PET/CT correctly characterized the tumor-node-metastasis system stage in 82 out of 86 studies (95.4%; 95% CI: 90.9% to 99.9%). PET alone and CT alone were found to be accurate in 71 out of 86 studies (82.6%; 95% CI: 74.5% to 90.6%) and 63 out of 86 studies (73.3%; 95% CI: 63.9% to 82.6%), respectively. Furthermore, the differences between PET/CT and either PET alone or CT alone were statistically significant (p<0.05). Overall, the study-based analysis of PET/CT for staging NPC demonstrated 48 true-positive, 2 false-negative, 34 true-negative and 2 false-positive studies. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of FDG-PET/CT studies for staging NPC were 96%, 94.4%, 95.4%, 96% and 94.4%, respectively. CONCLUSION: PET/CT is more accurate than PET alone or CT alone for the depiction of NPC. Fused PET/CT is a valuable imaging tool in patients for staging diagnosis of NPC.

Utility of FDG-PET for investigating unexplained serum AFP elevation in patients with suspected hepatocellular carcinoma recurrence.

UNLABELLED: The aim of this study was to evaluate the potential role of positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) in patients with unexplained rising serum alpha-fetoprotein (AFP) levels after the treatment of hepatocellular carcinoma (HCC). PATIENTS AND METHODS: Thirty-one FDG-PET studies were performed in 26 patients (age range, 45-83; 21 men and 5 women), who had undergone either surgical resection or interventional therapy for HCC, but were subsequently noted to have high AFP serum levels on routine follow-up examinations, although imaging studies and physical examinations were normal. The FDG-PET results were correlated with histological findings, as well as long-term radiological and clinical follow-up (shortest follow-up period after FDG-PET was 6 months). RESULTS: FDG-PET was abnormal in 22 of the 31 studies (71.0%) among the 26 patients. Intrahepatic lesions were detected in 20 of a total 30 lesions (66.7%) in 18 studies of FDG-PET among 26 patients. Ten FDG-PET studies among 9 patients identified one intrahepatic lesion, while 3 studies among 3 patients identified more than one intrahepatic lesion. Extrahepatic metastases were found in 9/31 studies of FDG-PET (29.0%) among 8 patients. These metastatic foci, composed of increased FDG accumulation, were identified in several locations; lung (4 studies among 4 patients), bone (2 studies among 2 patients) and the peritoneum (4 studies among 3 patients). Overall, FDG-PET for detecting HCC recurrence demonstrated 22 true-positives, 8 false-negatives, 1 true-negative and 0 false-positive results., The sensitivity, specificity and accuracy of FDG-PET for detecting HCC recurrence was 73.3%, 100% and 74.2%, respectively. CONCLUSION: When conventional examinations are normal, FDG-PET is a valuable imaging tool in patients who have rising AFP levels after HCC treatment. FDG-PET whole-body scan also provides an important and valuable imaging study for detecting extrahepatic metastasis.

Prevalence and risk of cancer of focal thyroid incidentaloma identified by 18F-fluorodeoxyglucose positron emission tomography for cancer screening in healthy subjects.

The aim of this study was to define the clinical prevalence and rate of malignancy of focal thyroid incidentaloma in a relatively large number of individuals with application of 18F-fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) in asymptomatic individuals. The subjects consisted of 4803 physical check-up examinees (2638 men, 2165 women; mean age+/-SD, 52.8+/-9 years old) with non-specific medical history. Whole-body FDG PET was performed on all patients. Focal hypermetabolic areas of thyroid, with an intensity equal to or exceeding the level of FDG uptake in the liver, were considered abnormal and interpreted as thyroid incidentaloma. Among the 4803 FDG PET examinations, thyroid incidentaloma was present in 60 examinations, among which, 50 had further examination with ultrasound-guided fine-needle aspiration (FNA), revealing 43 benign lesions and 7 papillary carcinomas. Of 7 examinees diagnosed with cancer, 2 had lymph nodes metastasis. The mean and standard deviation of standard uptake value (SUV) in benign and carcinoma was 2.6+/-1.01 and 6.7+/-3.66, respectively. Thyroid incidentaloma identified by FDG-PET occurred with a frequency of 1.2% (60/4803). Of the thyroid incidentalomas that underwent FNA and surgery, 14% (7/50) were found to be malignant. It is possible to differentiate benign from carcinoma of thyroid incidentalomas by the increased rate of glycolysis (SUV) in the carcinoma. The small size and moderate FDG uptake of thyroid incidentalomas per se cannot guarantee low risk in incidentally found thyroid cancers.

Application of PET and PEt/CT imaging for cancer screening.

The aim of this study was to evaluate the potential application of 18-fluorodeoxyglucose positron emission tomography (FDG PET) and PET/CT for cancer screening in asymptomatic individuals. The subjects consisted of 3631 physical check-up examinees (1947 men, 1684 women; mean age +/- SD, 52.1 +/- 8.2 y) with non-specific medical histories. Whole-body FDG PET (or PET/CT), ultrasound and tumor markers were performed on all patients. Focal hypermetabolic areas with intensities equal to or exceeding the level of FDG uptake in the brain were considered abnormal and interpreted as neoplasia. Follow-up periods were longer than one year. Among the 3631 FDG PET (including 1687 PET/CT), ultrasound and tumor markers examinations, malignant tumors were discovered in 47 examinees (1.29%). PET findings were true-positive in 38 of the 47 cancers (80.9%). In addition, 32 of the 47 cancers were screened with the PET/CT scan. PET detected cancer lesions in 28 of the 32 examinees. However, the CT detected cancer lesions in only 15 out of 32 examinees. The sensitivity of FDG PET in the detection of a wide variety of cancers is high. Most cancer can be detected with FDG PET at a resectable stage. CT of the PET/CT for localization and characteristics of the lesion showed an increased specificity of the PET scan. The use of ultrasound and tumor markers may complement the PET scan in cancer screening for hepatic and urologic neoplasms.

Colorectal cancer screening in asymptomatic adults: the role of FDG PET scan.

The aim of this study was to evaluate the potential application of 18F-fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) for colorectal cancer screening in asymptomatic individuals. The subjects consisted of 3210 physical check-up examinees (1736 men, 1474 women; mean age +/- SD, 53.2 +/- 8 y) with non-specific medical history. In the control group, 12 patients who had gastrointestinal symptoms with biopsy-proved colon carcinoma were recruited. Whole-body FDG PET was performed on all patients. Focal hypermetabolic areas with an intensity equal to or exceeding the level of FDG uptake in the brain and bladder were considered abnormal and interpreted as intraluminal neoplasia. Among the 3210 FDG PET examinations, advanced neoplasm was present in 20 examinations, including 2 tubular adenomas larger than 1 cm, 12 villous adenomas and 6 cancers. Of 6 examinees diagnosed with cancer, one had a Dukes stage A lesion, four had Dukes stage B lesion and one had a Dukes stage C lesion. In the control group, of 12 patients with biopsy-proved carcinoma followed by FDG PET scan, six had a Dukes stage B lesion, four had Dukes stage C lesion and two had a Dukes stage D lesion. The mean and standard deviation of standard uptake value (SUV) in colonic adenoma and carcinoma is 3.56 +/- 0.68 and 5.74 +/- 2.26, respectively. The sensitivity of using FDG PET in the detection of primary colorectal cancer is high. Primary colorectal cancer can be detected with FDG PET in a resectable stage. FDG PET could detect large size (> 0.7 cm) and pre-malignant change of colonic adenoma. It is possible to differentiate adenoma from carcinoma of colon by an increased rate of glycolysis (SUV) in carcinoma.