Metabolic activity measured on PET/CT correlates with clinical outcomes in patients with limb and girdle sarcomas.

OBJECTIVE: To explore the relationship between metabolic activity and outcome in patients with extremity sarcomas. METHODS: Between June 2004 and December 2011, 120 patients with newly diagnosed limb and girdle sarcomas underwent FDG-PET/CT for disease staging prior to curative intent treatment. The maximum standardized uptake value (SUV(max)) was measured for each primary tumor and correlated with outcome. Progression-free survival and overall survival (OS) were analyzed using the Kaplan-Meier method. RESULTS: Soft-tissue sarcomas were more frequent (68%) than bone (27%) or cartilage (5%) tumors. Median follow-up was 33.2 months. 51% of patients progressed during the follow-up interval and 38% died. SUV(max) was dichotomized with a cut-point of 10.3. Patients with SUV(max) < 10.3 had better DFS and OS compared with patients with SUV(max) ≥ 10.3 (P < 0.001 and P < 0.001, respectively [log-rank test]). Multivariate analysis confirmed that even after adjusting for age, sex, site, tumor type (bone vs. soft-tissue), grade, and stage; an SUV(max) ≥ 10.3 correlated with a twofold risk of progression and 2.4 times greater risk of death (hazard ratio [HR] 2.0, 95% CI, 1.1-3.7, and HR, 2.4, 95% CI, 1.1-4.9). CONCLUSION: SUV(max) is an independent adverse prognostic factor for both progression and OS in patients with extremity sarcomas.

Necrosis on FDG PET/CT correlates with prognosis and mortality in sarcomas.

OBJECTIVE: The purpose of this study was to determine if there is an association between necrosis as identified on staging (18)F-FDG PET/CT and overall survival (OS) and progression-free survival (PFS) in patients with sarcoma. MATERIALS AND METHODS: Sixty-six patients with newly diagnosed limb and girdle sarcoma underwent PET/CT at our institution between June 2004 and July 2009 for sarcoma staging before treatment with curative intent. The tumor maximum standardized up-take values (SUVmax), the presence of necrosis, and the volume of necrosis were measured for each primary tumor and correlated with follow-up data. PFS and OS were analyzed using the Kaplan-Meier method. Proportional hazards models were used to estimate hazard ratios. RESULTS: Median patient age was 49 years, and 51.6% of the patients were men. Sarcomas were categorized as soft tissue (69.2%), bone (23.5%), or other (7.3%). Mean follow-up time was 33.3 months. During the follow-up interval, 53% of patients experienced disease progression, and 40.9% died. There was a statistically significant relationship between the presence of necrosis and OS (by log-rank test, p = 0.001), as well as PFS (by log-rank test, p = 0.0001). Twenty-four-month OS was 96%, 65%, and 38% in patients with tumors with absence necrosis, those with presence of necrosis, and with necrosis volume greater than 50%, respectively. Forty-eight-month OS was 81% in patients with absence of necrosis and 41% in patients with presence of necrosis. Twelve-month PFS was 96%, 60%, and 42% in patients with tumors with absence of necrosis, those with presence of necrosis, and those with necrosis volume greater than 50%, respectively. Twenty-four-month PFS was 83%, 38%, and 22%, respectively, in these groups. CONCLUSION: The presence of necrosis and the volume of necrosis, as identified on the staging FDG PET/CT and after adjusting for SUVmax, are strong independent adverse prognostic factors for disease recurrence and death in patients with limb and girdle sarcomas.

Pancreatic involvement in Erdheim-Chester disease: Rare presentation of a rare disease.

Erdheim-Chester disease (ECD) as a rare non-Langerhans histiocytosis has various clinical manifestations. It is characterized histologically by infiltration of every organ, more commonly bone, retroperitoneum, cardiovascular and CNS systems with foamy, lipid -laden macrophage. Pancreatic involvement as a manifestation of this uncommon disease has very rarely been reported. Here we report a 73-year-old woman with ECD and pancreas involvement in CT, MRI and PET scans. We also aim to increase radiologist knowledge about considering ECD as a differential diagnosis for pancreas mass in the appropriate clinical situation.

Correlating metabolic activity on 18F-FDG PET/CT with histopathologic characteristics of osseous and soft-tissue sarcomas: a retrospective review of 136 patients.

OBJECTIVE: The objective of our study was to determine whether there is a statistically significant correlation between metabolic activity of osseous and soft-tissue sarcomas as measured by the maximum standardized uptake value (SUV(max)) on (18)F-FDG PET/CT and histopathologic characteristics such as mitotic counts, the presence of necrosis, and the presence of a myxoid component. MATERIALS AND METHODS: We retrospectively evaluated 238 consecutive patients with known soft-tissue or osseous sarcoma who underwent (18)F-FDG PET/CT for initial staging or assessment for recurrence of disease. The SUV(max) of each primary or of the most intense metastatic lesion was measured and was compared with the histologic data provided in the final pathology reports. RESULTS: Histopathologic data were available for 136 sarcomas. The median SUV(max) values of sarcomas with mitotic counts of less than 2.00 (per 10 high-power fields [HPF]), 2.00-6.99, 7.00-16.24, and 16.25 or greater were 5.0, 6.6, 10.3, and 13.0, respectively (p = 0.0003). The median SUV(max) for the sarcomas with necrosis (90 patients) was 8.6 and for those without necrosis (43 patients), 6.0 (p = 0.026). The median SUV(max) for the sarcomas without a myxoid component (118 patients) was 7.7 and with a myxoid component (16 patients) was 6.2 (p = 0.28). CONCLUSION: There was a statistically significant correlation between the mitotic count and the SUV(max) as well as between the presence of tumor necrosis and the SUV(max). Although a correlation between the presence of a myxoid component and SUV(max) was shown, it was not found to be statistically significant. These findings improve on the current information in the literature regarding the use of PET/CT for guidance in sarcoma biopsy. Correlating the SUV(max) with histologic markers that also feature prominently in major sarcoma grading systems may help improve the accuracy of grading and of prognostication by allowing the SUV(max) to potentially serve as a surrogate marker in these grading systems, particularly in cases in which there is interobserver disagreement in the pathologic diagnosis or in cases in which the sarcoma cannot be properly classified on the basis of histopathologic evaluation alone.

Spectrum of malignant pleural and pericardial disease on FDG PET/CT.

OBJECTIVE: The purpose of this article is to illustrate a wide spectrum of malignant primary and secondary pleural and pericardial diseases imaged with (18)F-FDG PET/CT. CONCLUSION: A wide variety of malignant pleural and pericardial diseases can be detected, staged, and monitored by FDG PET/CT. Although the PET/CT findings are often nonspecific, the aim of this atlas is to show that the spectrum of pleural and pericardial disease that can be evaluated with PET/CT is much broader than current literature would suggest. PET/CT readers and oncologists should be aware of the wide variety of malignancies that can affect the pleura and pericardium and some of the patterns of FDG uptake that can be observed in these cases.

Extraovarian primary peritoneal carcinoma: staging with 18F-FDG PET/CT.

A 69-year-old woman who presented with left lower quadrant abdominal pain and elevated serum cancer antigen 125 (CA-125) levels was referred for an MRI and an (18)F-FDG PET/CT to evaluate a suspicious abdominal mass seen on ultrasound. PET/CT showed extensive, intensely FDG-avid, omental and pelvic peritoneal thickening with no suspicious ovarian or colon masses. Based on the PET/CT results, the patient had extensive debulking surgery and histopathological evaluation revealed an extraovarian primary peritoneal carcinoma (EOPPC). (18)F-FDG PET/CT may be useful in differentiating EOPPC from other types of peritoneal carcinomatosis, and in determining the extent of the disease to better guide surgical management and improve long term outcomes.

FDG PET/CT in Initial Staging of Adult Soft-Tissue Sarcoma.

Soft-tissue sarcomas spread predominantly to the lung and it is unclear how often FDG-PET scans will detect metastases not already obvious by chest CT scan or clinical examination. Adult limb and body wall soft-tissue sarcoma cases were identified retrospectively. Ewing's sarcoma, rhabdomyosarcoma, GIST, desmoid tumors, visceral tumors, bone tumors, and retroperitoneal sarcomas were excluded as were patients imaged for followup, response assessment, or recurrence. All patients had a diagnostic chest CT scan. 109 patients met these criteria, 87% of which had intermediate or high-grade tumors. The most common pathological diagnoses were leiomyosarcoma (17%), liposarcoma (17%), and undifferentiated or pleomorphic sarcoma (16%). 98% of previously unresected primary tumors were FDG avid. PET scans were negative for distant disease in 91/109 cases. The negative predictive value was 89%. Fourteen PET scans were positive. Of these, 6 patients were already known to have metastases, 3 were false positives, and 5 represented new findings of metastasis (positive predictive value 79%). In total, 5 patients were upstaged by FDG-PET (4.5%). Although PET scans may be of use in specific circumstances, routine use of FDG PET imaging as part of the initial staging of soft-tissue sarcomas was unlikely to alter management in our series.

Incidental thyroid "PETomas": clinical significance and novel description of the self-resolving variant of focal FDG-PET thyroid uptake.

BACKGROUND: Recent series of incidental thyroid activity on fluorodeoxyglucose positron emission tomography (FDG-PET) in patients evaluated for nonthyroidal malignancy, which we refer to as a "PEToma," have suggested that such lesions are associated with a significant incidence of primary thyroid cancer. METHODS: We retrospectively reviewed 6457 FDG-PET scans performed on 4726 patients from May 2004 to March 2007. We reviewed the cases of patients whose PET or computed tomography (CT) radiology reports described PET uptake within the thyroid to identify incidence and malignant potential of PETomas and evaluate their clinical and histopathologic features. RESULTS: We found that 160 patients (3.4%) had incidental, abnormal FDG uptake in the thyroid gland, 103 of whom had focal uptake (the PEToma group). Of these patients, 50 (48%) underwent further investigations, including ultrasonography in 48, fine-needle aspiration cytology in 38 and computed tomography in 3. Ten patients underwent surgery, and papillary thyroid cancer was identified in 9. The remaining 53 patients with PETomas underwent no further investigation. Interestingly, 5 patients who had focal uptake within the thyroid showed either spontaneous resolution on repeat FDG-PET (self-resolving) or no focal lesion on subsequent ultrasonography (false-positive). CONCLUSION: The incidence of papillary thyroid cancer in the present series is similar to that in the literature. Although some patients will show self-resolving or false-positive focal thyroid uptake on FDG-PET, we believe that, if the patient's clinical status permits, the evaluation of patients with incidental thyroid PEToma should include ultrasonographic confirmation and fine-needle aspiration cytology.

Incidental Skeletal Findings on Sodium-fluoride Positron Emission Tomography: A Collection of Benign Tumors

Sodium-fluoride (NaF) positron emission tomography (PET) is a sensitive method to detect altered bone mineralization. Its increasing use in routine clinical practice for metastatic bone disease has also resulted in the detection or characterization of incidental benign bone lesions. A spectrum of NaF PET scan cases with benign bone tumors are presented in this article, including whole body PET bone scan and selected PET/computed tomography (CT), CT, or magnetic resonance imaging (MRI) of the region of interest. The reader will be able to improve their knowledge related to the clinical presentation of these entities, some are rare and recognize based on NaF PET and CT/MRI patterns by reviewing these cases.

FDG PET/CT imaging in primary osseous and soft tissue sarcomas: a retrospective review of 212 cases.

PURPOSE: The aims of this study are to evaluate the sensitivity of FDG PET/CT for detection of soft tissue and osseous sarcomas on the basis of FDG avidity. METHODS: We retrospectively evaluated 212 consecutive patients with known soft tissue or osseous sarcoma who had undergone a FDG PET/CT study for the initial staging or assessment of recurrence of disease. The maximum standardized uptake value (SUVmax) of each primary and/or most intense metastatic lesion was measured and compared with the histological data provided in the final pathological reports. An SUVmax of 2.5 or greater was considered positive for our analysis. RESULTS: Sufficient histopathological data were available for 160 soft tissue sarcomas and 52 osseous sarcomas. FDG PET/CT detected 93.9% of all sarcomas with a sensitivity of 93.7% for soft tissue sarcomas and 94.6% for osseous sarcomas. The sensitivities of the most common sarcoma histologies were 100% for leiomyosarcomas, 94.7% for osteosarcomas, 100% for Ewing's sarcomas, 88.9% for liposarcomas, 80.0% for synovial sarcomas, 100% for gastrointestinal stromal tumors, 87.5% for malignant peripheral nerve sheath tumors, 100% for fibroblastic and myoblastic sarcomas, and 100% for malignant fibrohistiocytic tumors. The receiver-operating characteristic curve revealed an area under the curve of 94% for the discrimination of low-grade and high-grade sarcomas imaged for initial staging by FDG PET/CT. CONCLUSION: The combined metabolic and morphological information of FDG PET/CT imaging allows high sensitivity for the detection of various sarcomas and accurate discrimination between newly diagnosed low-grade and high-grade sarcomas.

Correlation of the ERPF with the extraction fraction values of technetium-99m mercaptoacetyltriglycine.

OBJECTIVE: The objective of this study was to determine if a correlation exists between the effective renal plasma flow (ERPF) and the extraction fraction (EF) using 99mTc MAG3 in children. This EF has been previously described with 9mTc DTPA. However, the renal imaging agent of choice has become 9mTc MAG3. MATERIAL AND METHOD: The study was approved by The Children's Hospital of Philadelphia's institutional review board. Informed consent was also obtained A retrospective study of 29 children (16 males, 13 females) of ages 1 month to 19.5 years who underwent 99mTc MAG3 renal scintigraphy from September 2001 to December 2001 was analysed. EF values were calculated with and without attenuation correction in each kidney by determining the counts in a region of interest, correcting for background and comparing the counts with the injected dose. The EF was compared to the ERPF calculated using the Schlegel's method. The correlation between the EF and the ERPF corrected and non-corrected for soft tissue attenuation, were determined and were identified by using linear regression analysis. RESULTS: There was significant correlation between the ERPF and the EF with (r = 0.62, p < 0.05 on the left, r = 0.51, p = 0.005 on the right) than without attenuation correction (r = 0.54, p = 0.003 on the left, r = 0.42, p = 0.022 on the right). CONCLUSION: These results indicate a correlation of the ERPF calculated using the Schlegel's method with EF obtained from a 99mTc MAG3 renal scintigraphy. The EF may be the good alternative parameter for calculation of renal function, potentially more practical in pediatric patient and the ERPF for 99mTc MAG3 using the established software program based on Schlegel's formula.

Demonstration of excessive metabolic activity of thoracic and abdominal muscles on FDG-PET in patients with chronic obstructive pulmonary disease.

PURPOSE: The purpose of this study was to determine if an FDG-PET study was able to visualize muscle uptake of the chest and abdomen in patients with chronic obstructive pulmonary disease (COPD). METHODS: This study included 25 patients with COPD and 25 patients without COPD who had undergone a FDG-PET study. The nonattenuation-corrected images were used to determine the degree of FDG uptake in the intercostals, subscapular, abdominal rectus, and abdominal oblique muscles. The intensity of uptake in the muscles was rated on a 4-point grading scale with 1 being less, 2 the same, 3 slightly more, and 4 markedly more intense than the sternum. RESULTS: Thirteen patients with COPD demonstrated FDG activity in the intercostal muscles that was equal to or greater than the sternum and the tracer was demonstrated predominantly in the inferolateral chest wall (n = 8), the entire lateral chest wall (n = 2), the posteroinferior chest wall (n = 2), and the entire chest wall (n = 1). In all 13 patients with COPD who demonstrated FDG activity in the abdominal oblique muscles, the site of muscle activity was predominantly in the anteroinferior abdominal wall (n = 8), the lateral wall (n = 4), and the anterior wall (n = 1). In patients without known COPD, the frequency and intensity of uptake in the muscles were less than those with the disease. CONCLUSION: This study demonstrates the ability of FDG-PET imaging to assess muscle function in respiratory disorders and may prove to be of some value in further characterizing this disorder.

PET/Computed Tomography in the Diagnosis and Staging of Gastric Cancers.

Although there has been a reduction of the incidence and mortality of gastric cancer, it remains among the commonest causes of cancer-related death. Accurate staging and evaluation of treatment response are vital for management. PET is used to complement anatomic imaging in cancer management. PET/computed tomography (CT) has demonstrated its potential value for preoperative staging, evaluation of response to therapy, and detection of recurrence. Not all types of gastric cancers have a high affinity for fluorodeoxyglucose. PET/CT in the evaluation and staging of gastric cancer is not established, but studies indicate that there may be an evolving role for this imaging modality.

Penile metastasis from rectal cancer by PET/CT.

It is extremely rare for rectal tumors to metastasize to the penis, and when it occurs, it is associated with poor prognosis. The appearance of penile metastasis from rectal primary tumor on PET imaging has not been widely reported. We report a case of a 70-year-old man with previous history of treated stage III adenocarcinoma of the rectum 26 months ago. The restaging 18F-FDG PET/CT scan demonstrated a hypermetabolic mass at the base of his penile shaft. This lesion was confirmed on core biopsy to be a metastatic adenocarcinoma of colorectal origin consistent with the known primary rectal tumor.

Dual time point 18F-FDG PET for the evaluation of pulmonary nodules.

UNLABELLED: 18F-FDG PET has reached widespread application in the assessment of pulmonary nodules. This study compares the diagnostic accuracy of standard 18F-FDG PET scanning with those of dual time point 18F-FDG PET scanning. METHODS: Thirty-six patients (21 women, 15 men; mean age, 67 y; range, 36-88 y) with 38 known or suspected malignant pulmonary nodules underwent PET of the thorax at 2 time points: scan 1 at 70 min (range, 56-110 min) and scan 2 at 123 min (range, 100-163 min) after the intravenous injection of 2.5 MBq 18F-FDG per kilogram of body weight. All scanning was performed on a dedicated C-PET scanner. The mean interval between the scans was 56 min (range, 49-64 min). Regions of interest were overlaid onto each fully corrected image in the areas of the radiographically known lung densities. The standardized uptake values (SUVs) were calculated for both time points. RESULTS: Surgical pathology and follow-up revealed 19 patients with 20 malignant tumors, whereas 16 patients had benign lesions. The tumor SUVs (mean +/- SD) were 3.66 +/- 1.95 (scan 1) and 4.43 +/- 2.43 (scan 2) (20.5% +/- 8.1% increase; P < 0.01). Four of 20 malignant tumors had SUVs of <2.5 on scan 1 (range, 1.12-1.69). Benign lesions had SUVs of 1.14 +/- 0.64 (scan 1) and 1.11 +/- 0.70 (scan 2) (P = not significant). Standard PET scanning (single time point) with a threshold SUV of 2.5 (at time point 1) reached a sensitivity of 80% and a specificity of 94%; dual time point scanning with a threshold value of 10% increase between scan 1 and scan 2 reached a sensitivity of 100% with a specificity of 89%. CONCLUSION: Dual time point 18F-FDG PET results in a very high sensitivity and specificity for detection of malignant lung tumors.

Positron emission tomography imaging in nonmalignant thoracic disorders.

The role of the fluorodeoxyglucose (FDG) technique positron emission tomography (PET) is well established in the management of patients with lung cancer. Increasingly, it is becoming evident that FDG-PET can be effectively employed to diagnose a variety of benign pulmonary disorders. Knowledge of such applications further expands the domain of this powerful modality and further improves the ability to differentiate benign from malignant diseases of the chest. We describe pertinent technical factors that substantially contribute to optimal imaging of the thoracic structures. Particularly, the complementary role of attenuation correction (AC) to that of non-AC images is emphasized. We further outline the need for and the state of the art for co-registration of PET and anatomic images for diagnostic and therapeutic purposes. We then review patterns of physiologic uptake of FDG in thoracic structures, including the lung, the heart, the aorta and large arteries, esophagus, thymus, trachea, thoracic muscles, bone marrow, and joints and alterations following radiation therapy to the thorax. A great deal of information is provided with regard to differentiating benign from malignant nodules and in particular, we emphasize the role of dual time point imaging and partial volume correction for accurate assessment of such lesions. Following a brief review of the diagnostic issues related to the assessment of mediastinal adenopathies, the role of FDG-PET imaging in environment-induced lung diseases, including pneumoconiosis, smoking, and asthma are described. A large body of information is provided about the role of this technology in the management of patients with suspected infection and inflammation of the lungs such as acquired immunodeficiency syndrome, fever of unknown origin, sarcoidosis, chronic granulomatous disease and monitoring the disease process and response to therapy. Finally, the value of FDG-PET in differentiating benign from malignant diseases of the pleura including asbestosis-related disorders is described at the conclusion of this comprehensive review.

Supranormal renal function in unilateral hydronephrotic kidney can be avoided.

INTRODUCTION: There are reports and controversy in the literature of supranormal (defined as >55%) differential renal function (DRF) in the hydronephrotic kidney in children with unilateral hydronephrosis. It is not confirmed whether supranormal DRF is an artifact or a true finding. In patients in whom the relative renal function deteriorates, relief of obstruction becomes surgically necessary and if this artifact can be removed. Supranormal function in an obstructed kidney is confusing and there is no consensus on how to manage these patients. There is no agreement if this is a true entity or an artifact. We wanted to address this issue by reporting our experience. METHODS: We reviewed all the consecutive cases from August 2000 to October 2001 who were studied in our center with the diagnosis of unilateral renal obstruction for confirmation or evaluation of DRF. All patients had MAG-3 studies that were interpreted by experienced nuclear medicine physicians. The DRF were measured within the first to second minute of the MAG-3 injection. Regions of interest were drawn by the imaging software and the images were corrected for background counts by drawing regions of interest 2 pixels away from the edge of the renal cortex. RESULTS: Fifty-seven patients were confirmed to be obstructed unilaterally; 41 (72%) patients had obstructive lesions in the left kidney and 16 (28%) in the right kidney. There was no case of supranormal DRF in the obstructed kidneys in our study. CONCLUSION: The supranormal renal function, as noted in some reports in the literature, was not seen in any patients at our institution. We believe that this entity is an artifact and can be avoided by using MAG-3 and projecting regions of interest by computer software; we plan to start analyzing multiple algorithms in phantoms with different ROI selection for background analysis.

Incidental detection of colon cancer by FDG positron emission tomography in patients examined for pulmonary nodules.

PURPOSE: Fluorodeoxyglucose (FDG) positron emission tomographic (PET) imaging has been used extensively to diagnose cancer with high rates of sensitivity and specificity. One of its applications is to distinguish benign from malignant pulmonary nodules. It is common to observe colonic uptake on whole-body FDG-PET images. Because patients with lung cancer also tend to be in the age group with the highest incidence of colon cancer, the authors tried to assess the efficacy of FDG-PET for detecting occult colon cancer in patients referred for the evaluation of lung nodules. METHODS: The records of 500 consecutive patients referred for the evaluation of pulmonary nodules were reviewed retrospectively. Among the patients, 197 had no previous clinical or radiographic evidence of abnormalities in the gastrointestinal tract, and none had been found to have any cancer before undergoing an FDG-PET study. All colon lesions were verified either by histologic analysis or by clinical course. RESULTS: Among the 197 patients analyzed, 59 had diffuse colonic uptake in various segments of the colon. Seventeen of the patients had focal colonic uptake, five of which were proved to be colon cancer. CONCLUSIONS: The routine use of FDG PET to characterize lung lesions significantly increases the probability of detecting unexpected extrathoracic disease. In these patients, the incidental finding of colon cancer had an important effect on their treatment and may prove to be very cost-effective.

18F-FDG PET/CT superior to serum CEA in detection of colorectal cancer and its recurrence.

The aim of this study was to examine whether positron emission tomography (PET)/computed tomography (CT) can detect more cases of colorectal cancer (CRC) than serum carcinoembryonic antigen (CEA), both at initial staging and during surveillance for recurrence. A retrospective review of 639 CRC patients imaged with PET/CT was performed. PET/CT was superior to serum CEA in detecting CRC, identifying 2.5 times as many CRC at initial staging compared to serum CEA and 1.5 times as many CRC recurrences. The current guideline recommendations of utilizing PET/CT only in the context of a rising serum CEA will miss more than one third of all CRC recurrences.