FDG PET/CT and Conventional Imaging Methods in Cancer of Unknown Primary: an Approach to Overscanning / 대한핵의학회잡지

PURPOSE: To compare the performance of fluorine-18 fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) with conventional imaging methods (CIM), including computed tomography (CT), magnetic resonance imaging (MRI), and mammography (MMG) in cancer of unknown primary (CUP).METHODS: A total of 36 patients with CUP, who referred to our clinic for a FDG PET/CTscan, were enrolled in this study. Thirty of the patients were also examined through either diagnostic CT/MRI and/or MMG. The diagnostic performance of both methods for the primary cancer location was analyzed. The results of FDG PET/CT and CIM were compared based on the standard reference of the histopathology and/or clinical and laboratory follow-up.RESULTS: The primary cancer locations were detected in 24 patients (66.6%, 24/36) by FDG PET/CT, whereas CIM identified the locations in 16 patients (53.3%, 16/30). Sensitivity, specificity, PPV, NPV, and accuracy rates of the detection of the primary tumor localizations were as follows: 83, 70, 89, 58, and 79% for FDG PET/CT; 70, 62, 84, 42, and 68% for CIM, respectively. There was no statistical significance between modalities regarding any of the categories in 30 patients.CONCLUSION: FDG PET/CT detected the primary tumors of the patients with CUP more than CIM did. However, the difference between them was not found to be statistically significant. It may be considered that FDG PET/CT scan can be performed as a first-line tool in the initial diagnosis of the patients with CUP and to add radiodiagnostic imaging in selective cases.We conclude that if the first-line examination of a CUP patient has been already performed by a CIM and the result was negative or inconclusive, FDG PET/CT can be considered to avoid unnecessary imaging procedures.

Detection of Solitary Axillary Lymph Node Metastases from Hürthle Cell Carcinoma of the Thyroid on ¹⁸F-FDG PET/CT / 대한핵의학회잡지

Thyroid carcinoma is the most common neoplasm of endocrine malignancies. Differentiated thyroid carcinoma (DTC) constitutes 90% of the thyroid carcinomas, rest being medullary thyroid carcinoma (MTC), and anaplastic thyroid carcinoma (ATC). Distant metastases occur in up to 10% of patients with DTC. Metastases to axillary lymph nodes (ALN) are very rare. As per literature, only 25 cases have been reported. We report an unusual case of 47-year-old male with Hürthle cell carcinoma of the thyroid presenting with a solitary axillary lymph node metastasis 17 years after thyroidectomy, along with review of literature.

Evaluating the Predictive Ability of Initial Staging F-18 FDG PET/CT for the Prognosis of Non-HodgkinMalignant Lymphoma Patients Who Underwent Stem Cell Transplantation / 대한핵의학회잡지

OBJECTIVES: This study aimed to determine the value of clinical prognostic factors and semiquantitative metabolic parameters from initial staging fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (F-18 FDG PET/CT) in non-Hodgkin lymphoma (NHL) patients treated with stem cell transplantation (SCT).METHODS: A total of 39 malignant lymphoma patients who underwent initial staging F-18 FDG PET/CT were enrolled in this study. SUVmax, MTV_wb, and TLG_wb were measured during the initial staging PET/CT. Receiver operating characteristic curve (ROC) analysis was adopted to dichotomize continuous variables. Log-rank test and Cox proportional hazard regression analysis were used to evaluate disease-free survival (DFS) rate.RESULTS: Among the 39 patients with malignant lymphoma, 17 (43.6%) had a relapse. For several clinical factors such as age, ECOG performance score, AMC/ALC score, stages, and revised International Prognostic Index score, differences between the two dichotomized groups were statistically insignificant. In univariate analysis, DFS estimates were 71.0 ± 7.8 months and 18.0 ± 5.9 months in high-SUVmax and low-SUVmax group, respectively (P < 0.01). For MTV_wb, DFS estimates were 46.6 ± 12.4 months and 69.1 ± 8.5 months in high-MTV_wb and low-MTV_wb group, respectively (P = 0.12). For TLG_wb, DFS estimates were 65.3 ± 7.5 months and 13.7 ± 8.6 months in high-TLG_wb and low-TLG_wb group, respectively (P = 0.02). In Cox proportional hazard regression analysis, only MTV_wb showed statistical significance (HR 3.01, 95% CI 1.04−8.74, P = 0.04).CONCLUSION: In NHL patients treated with SCT, the MTV_wb of initial staging F-18 FDG PET/CTwas an independent prognostic factor.

Incidental Detection of Peri-Renal Hemorrhage on F-18 FDG PET/CT Imaging in a Patient with Polycystic Kidney Disease / 대한핵의학회잡지

A 72-year-old male patient with a history of polycystic kidney disease and lung malignancy underwent F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) for the evaluation of tumor recurrence. The FDG PET/CT and subsequent non-enhanced CT scans revealed a hemorrhage in the peri-renal space of the left original kidney. Interesting in this case was the incidental detection of unexpected peri-renal hemorrhage during an oncologic assessment with FDG PET/CT.

Difference in F-18 FDG Uptake After Esophagogastroduodenoscopy and Colonoscopy in Healthy Sedated Subjects / 대한핵의학회잡지

PURPOSE: We aimed to evaluate the difference in fluorodeoxyglucose (FDG) uptake in sedated healthy subjects after they underwent esophagogastroduodenoscopy (EGD) and colonoscopy procedures.METHODS: The endoscopy group (n = 29) included healthy subjects who underwent screening via F-18 FDG positron emission tomography/computed tomography (PET/CT) after an EGD and/or colonoscopy under sedation on the same day. The control group (n = 35) included healthy subjects who underwent screening via PET/CT only. FDG uptake in the tongue, uvula, epiglottis, vocal cords, esophagus, stomach, duodenum, liver, cecum, colon, anus, and muscle were compared between the two groups.RESULTS: Maximum standardized uptake value (SUVmax) in the tongue, pharynx, larynx, and esophagus did not significantly differ between the endoscopy and control groups. In contrast, mean SUVmax in the whole stomach was 18 % higher in the endoscopy group than in the control group (SUVmax: 2.96 vs. 2.51, P = 0.010). In the lower gastrointestinal track, SUVmax from the cecum to the rectum was not significantly different between the two groups, whereas SUVmax in the anus was 20% higher in the endoscopy group than in the control group (SUVmax: 4.21 vs. 3.50, P = 0.002). SUVmax in the liver and muscle was not significantly different between the two groups. Mean volume of the stomach and mean cross section of the colon was significantly higher in the endoscopy group than in the control group (stomach: 313.28 cm³ vs. 209.93 cm³, P < 0.001, colon: 8.82 cm² vs. 5.98 cm², P = 0.001).CONCLUSIONS: EGD and colonoscopy under sedation does not lead to significant differences in SUVmax in most parts of the body. Only gastric FDG uptake in the EGD subjects and anal FDG uptake in the colonoscopy subjects was higher than uptake in those regions in the control subjects.

Bilateral Renal Metastasis of Hürthle Cell Thyroid Cancer with Discordant Uptake Between I-131 Sodium Iodide and F-18 FDG / 대한핵의학회잡지

Renal metastasis of thyroid cancer is extremely rare. We report the case of a 62-year-old woman with Hürthle cell thyroid cancer (HCTC) with lungs, bones, and bilateral kidneys metastases. The renal metastatic lesions were clearly demonstrated by ¹³¹I whole body scan (WBS) with SPECT/CT. However, they exhibited false-negative results in ¹⁸F-FDG PET/CT, kidney ultrasonography, and contrast-enhanced CT scan. The findings imply that tumors have low glucose metabolism and are able to accumulate radioiodine, which is not commonly found in the relatively aggressive nature of HCTC. The patient received two sessions of 200 mCi ¹³¹I therapy within 6 months duration. There was complete treatment response as evaluated by the second post-therapeutic ¹³¹I SPECT/CT and serum thyroglobulin. To our knowledge, renal metastasis from HCTC with positive ¹³¹I but negative ¹⁸F-FDGuptake has not been reported in the literature. This case suggests that ¹³¹I SPECT/CTis useful for lesion localization and prediction of ¹³¹I therapy response.

Ratio of Mediastinal Lymph Node SUV to Primary Tumor SUV in ¹⁸F-FDG PET/CT for Nodal Staging in Non-Small-Cell Lung Cancer / 대한핵의학회잡지

PURPOSE: Following determination of the maximum standardized uptake values (SUVmax) of the mediastinal lymph nodes (SUV-LN) and of the primary tumor (SUV-T) on ¹⁸F-FDG PET/CT in patients with non-small-cell lung cancer (NSCLC), the aim of the study was to determine the value of the SUV-LN/SUV-T ratio in lymph node staging in comparison with that of SUV-LN.METHODS: We retrospectively reviewed a total of 289 mediastinal lymph node stations from 98 patients with NSCLC who were examined preoperatively for staging and subsequently underwent pathologic studies of the mediastinal lymph nodes. We determined SUV-LN and SUV-R for each lymph node station on ¹⁸F-FDG PET/CT and then classified each station into one of three groups based on SUV-T (low, medium and high SUV-T groups). Diagnostic performance was assessed based on receiver operating characteristic (ROC) curve analysis, and the optimal cut-off values that would best discriminate metastatic from benign lymph nodes were determined for each method.RESULTS: The average of SUV-R of malignant lymph nodes was significantly higher than that of benign lymph nodes (0.79±0.45 vs. 0.36±0.23, P<0.0001). In the ROC curve analysis, the area under the curve (AUC) of SUV-R was significantly higher than that of SUV-LN in the low SUV-T group (0.885 vs. 0.810, P= 0.019). There were no significant differences between the AUCs of SUV-LN and of SUV-R in the medium and high SUV-T groups. The optimal cut-off value for SUV-R in the low SUV-T group was 0.71 (sensitivity 87.5 %, specificity 85.9 %).CONCLUSIONS: The SUV-R performed well in distinguishing between metastatic and benign lymph nodes. In particular, SUV-R was found to have a better diagnostic performance than SUV-LN in the low SUV-T group.

Unusual Contiguous Soft Tissue Spread of Advanced Malignant Mesothelioma Detected by FDG PET/CT / 대한핵의학회잡지

Malignant pleural mesothelioma (MPM) is a tumor of mesodermal origin that arises from the serosa of the pleura, peritoneum, pericardium or tunica vaginalis. MPM is well known to have a poor prognosis with a median survival time of 12 months. Accurate diagnosis, staging and restaging of MPM are crucial with [18F] flurodeoxy-D-glucose positron emission tomography (FDG PET/CT) playing an increasingly important role. Here we report a case of MPM with unusual contiguous soft tissue spread of the tumor along the dermal and fascial planes characterized by PET/CT. Given that the loco-regional tumor in the thorax was under control on PET/CT, the death of the patient was most likely associated with physiologic or metabolic causes associated with an extra-thoracic tumor.

Correlation of Molecular Subtypes of Invasive Ductal Carcinoma of Breast with Glucose Metabolism in FDG PET/CT: Based on the Recommendations of the St. Gallen Consensus Meeting 2013 / 대한핵의학회잡지

PURPOSE: This study aimed to investigate the relationship between the SUVmax of primary breast cancer lesions and the molecular subtypes based on the recommendations of the St. Gallen consensus meeting 2013.METHODS: Clinical records of patients who underwent F-18 FDG PET/CT for initial staging of invasive ductal carcinoma (IDC) of SUVmax was correlated with the molecular subtypes defined by the St. Gallen Consensus Meeting 2013, i.e., luminal A-like (LA), luminal B-like HER2 negative (LBHER2−), luminal Blike HER2 positive (LBHER2+), HER2 positive (HER2+), and triple negative (TN), and with the clinicohistopathologic characteristics.RESULTS: The molecular subtype was LA in 38 patients, LBHER2− in 72, LBHER2+ in 21, HER2+ in 30, and TN in 22. The mean SUVmax in the LA, LBHER2−, LBHER2+, HER2+, and TN groups were 4.5 ± 2.3, 7.2 ± 4.9, 7.2 ± 4.3, 10.2 ± 5.5, and 8.8 ± 7.1, respectively. Although SUVmax differed significantly among these subtypes (p < 0.001), the values showed a wide overlap. Optimal cut-off SUVmax to differentiate LA from LBHER2−, LBHER2+, HER2+ and TN were 5.9, 5.8, 7.5, and 10.2 respectively, with area under curve (AUC) of 0.648, 0.709, 0.833, and 0.697 respectively. The cut-off value of 5.9 yielded the highest accuracy for differentiation between the LA and non-LA subtypes, with sensitivity, specificity, and AUC of 79.4 %, 57.9 %, and 0.704 respectively.CONCLUSION: The SUVmax showed a significant correlation with the molecular subtype. Although SUVmax measurements could be used along with immunohistochemical analysis for differentiating between molecular subtypes, its application to individual patients may be limited due to the wide overlaps in SUVmax.

FDG-PET Identification of Infected Pulmonary Artery Conduit Following Tetralogy of Fallot (TOF) Repair / 대한핵의학회잡지

Tetralogy of Fallot (TOF) is one of the most common forms of cyanotic congenital heart disease usually managed by serial surgical repairs. The repaired prosthetic valve or conduit is susceptible to life-threatening infection. FDG-PET is an effective alternative to evaluate the source of infection when other examinations are inconclusive. We report an unusual case of an infected pulmonary artery conduit after TOF repair although the echocardiogram was negative for vegetation, which was later confirmed by surgery and pathology. The case highlights the role of FDG-PETas a problem-solving tool for potential endocarditis and cardiac device infection cases after complex cardiac surgery.