Marc Hickeson

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. Ewings 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.

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.

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.

Myeloid sarcoma presenting as an anterior mediastinal mass invading the pericardium: Serial Imaging With F-18 FDG PET/CT.

Myeloid sarcoma is a tumor formed by extramedullary accumulation of myeloblasts or immature myeloid cells. These tumors can develop in lymphoid organs, bone, skin, soft tissue, and other organs, and may precede or occur concurrently with acute myeloid leukemia. This is a case of a 42-year-old man who presented with a 2-week history of cough and shortness of breath on exertion. A computed tomography (CT) scan showed a large mediastinal mass and pericardial effusion. An F-18 fluorodeoxyglucose positron emission tomography-CT scan showed intense fluorodeoxyglucose (FDG) uptake in the mediastinal mass with invasion of the parietal pericardium. Biopsy of the mediastinal mass and pericardium revealed myeloid sarcoma. The pericardial effusion was drained and the patient was treated with high-dose cytosine arabinoside (HiDAC) chemotherapy. A follow-up positron emission tomography-CT was done 2 months after the last cycle, showing poor response to therapy and significant progression of disease with invasion through the anterior chest wall. Myeloid sarcoma can be added to the differential diagnosis of F-18 FDG avid anterior mediastinal masses, as well as F-18 FDG uptake in the pericardium.

Intensity of FDG uptake is not everything: synchronous liposarcoma and fibrous dysplasia in the same patient on FDG PET-CT imaging.

A growing number of studies have demonstrated the usefulness of FDG PET-CT in the preoperative assessment of soft tissue sarcomas. We report a case of a patient with a known low-grade liposarcoma demonstrating only mild hypermetabolism on a FDG PET-CT study. An incidental osseous lesion was found in the distal tibia of the same extremity during the initial workup. This tibial lesion was significantly more intense on the FDG PET-CT study than the primary sarcoma. Further investigation showed this to be an unexpected benign fibrous dysplasia. We present this case as an example of the discrepancy of FDG activity, which may exist between truly malignant and benign lesions that may arise from soft tissue and osseous structures. A benign process should remain in the differential diagnosis for hypermetabolic lesions when evaluating a case of known malignancy, especially when the degree of uptake of that lesion differs significantly from that of the primary lesion.

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.

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.

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.

Malignant perivascular epithelioid cell tumor (PEComa) of the uterus: serial imaging with F-18 FDG PET/CT for surveillance of recurrence and evaluation of response to therapy.

Abstract: This is a case of a 52-year-old woman who underwent a hyster-ectomy to treat a large uterine perivascular epithelioid cell tumor. She wasfollowed with serial F-18 FDG PET/CT scans due to positive surgicalmargins and vascular invasion on pathology. Initial surveillance PET/CTperformed 6 months post surgery was negative; however, a second surveil-lance PET/CT performed 12 months post surgery showed an intenselyFDG-avid recurrence in the pelvic surgical site. The patient received localradiotherapy, 2 cycles of taxol and carboplatin, and was placed on imatinibmesylate (Gleevec). A final PET/CT performed 6 months after initiation oftherapy showed rapidly disseminating metastatic disease and the patient died1 month later. This rare report highlights a potentially new utility of F-18FDG PET/CT for surveillance of recurrence of a malignant uterine perivas-cular epithelioid cell tumor, as well as for evaluation of response to therapy. Key Words: malignant perivascular epithelioid cell tumor, PEComa,uterus tumors, FDG, PET/CT(

Interesting image. Maffucci syndrome with extraosseous chondrosarcoma imaged with F-18 FDG PET-CT.

Abstract:Maffucci syndrome is a rare congenital mesodermal dysplasia, characterized by multiple enchondromas and hemangiomas. The syndrome is nonhereditary, and the etiology remains unknown. We present a 42-year-old man with known Maffucci syndrome who had a fluoro-deoxy-glucose positron emission to