Fluorodeoxyglucose PET in the evaluation of amputations for soft tissue sarcoma

[Contribution of FDG-PET in the management of pediatric sarcomas in 2011]

FDG-PET has boomed in recent years for diagnosis, staging and the search for recurrence of a large number of tumors. This is particularly true for soft tissue sarcomas and musculoskeletal sarcomas, for which the first publications on the potential role of FDG-PET dating back to the early 1990s. The majority of published studies on adult sarcomas confer, possibly a mixed population. Studies dedicated to pediatrics population are much rarer. The "Standards, Options and Recommendations" of the French Federation of Anticancer Centers published in 2003 on "The use of FDG-PET in oncology" and make recommendations and expert advices as part sarcomas of adult patients. After a first part dedicated to the particular interpretation of FDG PET in children, the purpose of this paper is to review the potential contribution of this exam in the treatment of pediatric sarcomas.

PET imaging for pediatric oncology: an assessment of the evidence

Positron emission tomography (PET) has shown potential benefits when used in therapeutic clinical trials for children with cancer. However, existing trials are limited in scope with small numbers of patients and varied observations, making accurate conclusions about the usefulness of PET scanning impossible. This review examines PET and its applications in pediatric oncology. While evidence is limited, there appears to be a basis for rigorous evaluation of this imaging modality before widespread application without validation from clinical trials.

Role of PET/PET-CT in the management of sarcomas

Positron emission tomography (PET) is a functional diagnostic imaging technique that provides very different information from that obtainable with other imaging modalities. The most widely used radiotracer is F-18 fluoro-2-deoxy-D-glucose (FDG), which is an analog of glucose. The FDG uptake in cells is directly proportional to glucose metabolism, which is increased many times in malignant cells. FDG-PET is now the standard of care in initial staging, monitoring the response to therapy and management of various cancers (e.g., breast cancer, lung cancer and lymphoma). However, the paucity of anatomical landmarks on PET images makes a consistent hardware fusion to anatomical cross-sectional data extremely useful. The introduction of combined PET-computer tomography (CT) scanners, which provide not only functional, but also structural information leading to a detection of subcentimeter lesions, made this technique useful in the early detection of the disease process and decreasing false-positive lesions. The aim of this article is to review the clinical applications (i.e., diagnosis, staging, evaluation of treatment response and restaging) using PET in patients with bone and soft-tissue sarcoma.

Sarcomes des tissus mous des extrémités. Rôle de l'imagerie dans la prise en charge initiale

Soft tissue sarcomas are uncommon heterogeneous group of tumour derived from mesenchym. The most common location is the lower extremity, but they can occur in the upper extremity, and abdominal and chest walls. The first radiological evaluation may include plain films and ultrasonography in viewing to assess the probability of soft tissue sarcomas. MRI with contrast is the main modality to evaluate these lesions and choose which part of tumour must be biopsied. Computer tomography (CT) is secondary used to perform core needle biopsy and detect lung metastases. The role of PET begins to be more clear in case of need global assessment before radical surgery. A multidisciplinary approach is essential to perform rational treatment planning and avoid partial surgery.

[Soft sarcoma tissue of extremities: medical imagery in post-therapeutic follow-up]

After treatment of primary soft tissue sarcoma, a third of patients will develop local or distant (lung in 90% of cases) recurrence. For an individual patient, the issue of cancer recurrence is a binary event. However, when developing surveillance strategies for large groups of patients, knowledge of the risks (tumor biology, natural history of the disease), the benefits (potential efficacy of salvage therapy) and diagnosis test performances is necessary to formulate a rationale and resource effective follow-up algorithm.

Diagnóstico de recurrencia mediante FDG-PET en un caso clínico de schwannoma maligno

The peripheral nerve sarcoma, also called malignant schwannoma, is originally a soft tissue sarcoma. It is mainly located in the peripheral sheath nerve of the limbs and usually infiltrates the nerve fibres. We present the case of a thirty year old woman with a malignant schwannoma in her left leg sciatic nerve who had been treated on several occasions. An 18-FDG positron emission tomography was performed to evaluate the management of the patient. It showed regional recurrence, which required leg amputation. The pathological result has confirmed the PET diagnosis. PET can be a useful technique to detect recurrence for this kind of tumor, mainly in patients who have been previously radiated when the MRI is insufficient to perform a differential diagnosis between postirradiation fibrosis and tumoral recurrence, allowing for suitable therapeutic management of the patient.

Musculoskeletal system

Diagnostic imaging has played a major role in the evaluation of patients with cancers of the bone and soft tissue. The imaging modalities have included radiography, computed tomography, magnetic resonance imaging, and bone scintigraphy. Current experience suggests that functional imaging with positron emission tomography (PET) and [F-18]fluorodeoxyglucose (FDG) may also have an important role in the imaging evaluation of patients with bone and soft tissue sarcoma, including guiding biopsy, detecting local recurrence in amputation stumps, detecting metastatic disease, predicting and monitoring response to therapy, and assessing for prognosis. Prospective studies with large patient groups will be essential to define the exact diagnostic role of FDG PET in this clinical setting, which should also include an evaluation of the cost-effectiveness and the short-term and long-term benefits in clinical decision making and management. In this article, we review the diagnostic utility of dedicated PET and PET combined with computed tomography imaging system in the evaluation of patients with bone and soft tissue malignancies.

FDG-PET for detection of recurrences from malignant primary bone tumors: comparison with conventional imaging

BACKGROUND

The aim of this study was to assess the diagnostic ability of positron emission tomography using 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG-PET) in the detection of recurrences from malignant primary bone tumors compared with conventional imaging.

PATIENTS AND METHODS

In 27 patients (6 osteosarcomas, 21 Ewing's sarcomas), 41 FDG-PET examinations performed for diagnosis or exclusion of recurrent disease were evaluated. Conventional imaging techniques consisted of magnetic resonance imaging of the primary tumor site, thoracic computed tomography, and Tc-99m methylene diphosphonate bone scintigraphy. The reference methods were the histopathological analysis and/or the clinical and imaging follow-up.

RESULTS

In 25 examinations reference methods revealed 52 sites of recurrent disease (local n = 7; distant: osseous n = 22, pulmonary n = 13, soft tissue n = 10). On an examination-based analysis FDG-PET had a sensitivity of 0.96, a specificity of 0.81 and an accuracy of 0.90. Corresponding values for conventional imaging were 1.0, 0.56 and 0.82.

CONCLUSIONS

The sensitivity, specificity and accuracy of FDG-PET in the detection of recurrences from osseous sarcomas are high. On an examination-based analysis, FDG-PET had a not significantly lower sensitivity in comparison with conventional imaging. However, FDG-PET showed a small advantage in the detection of osseous and soft-tissue recurrences compared with conventional imaging.