Functional imaging techniques for evaluation of sarcomas

Diagnostic Performance of Elastography in Malignant Soft Tissue Tumors: A Systematic Review and Meta-analysis

Malignant soft tissue tumors (STTs) are often mistaken for benign tumors, leading to inappropriate treatment including unplanned resection. Elastography, as a non-invasive measurement of tissue mechanical properties, makes use of the different soft tissue elasticity in diverse pathologies to generate information that can be used for diagnostic purposes. Elastography for STTs carries important information that is helpful in differentiating malignant and benign masses. The present study was undertaken to systematically review existing trials on the reliability of elastography in assessment of malignant STTs. A comprehensive literature exploration of the PubMed, EMbase and China National Knowledge Infrastructure databases was conducted for published articles involving the application of elastography in distinguishing malignant STTs. The diagnostic performance of elastography was evaluated with pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio and area under the summary receiver operating characteristic curve. Publication bias was also evaluated. This meta-analysis enrolled 18 eligible studies with a total of 1420 patients. The overall number of reported STTs was 1569, of which 478 were classified as positive and 1091 as negative at elastography. The pooled sensitivity, specificity, positive likelihood ratio and negative likelihood ratio of elastography were 0.82 (95% confidence interval: 0.74-0.87), 0.80 (0.71-0.86), 3.99 (2.65-6.01) and 0.23 (0.15-0.34), respectively. The diagnostic odds ratio and area under the curve were 17.36 (8.28-36.38) and 0.88 (0.84-0.90), respectively (Glas et al. 2003). The results of meta-regression analysis revealed that the total number of patients and prevalence of malignant STTs were significant factors in sensitivity, and the year of publication, total number of patients and index test were significant factors affecting study heterogeneity for specificity (p < 0.05). No significant publication bias was observed. This meta-analysis indicates that ultrasound elastography achieves relatively good performance in discriminating between malignant and benign STTs. Nevertheless, further research is needed to verify this finding.

Preliminary clinical assessment of dynamic carbon-11 methionine positron-emission tomography/computed tomography for the diagnosis of the pathologies in patients with musculoskeletal lesions: a prospective study

Background

This study prospectively assessed the diagnostic capacity of dynamic carbon-11 methionine (C-11 MET) positron-emission tomography (PET)/computed tomography for the diagnosis of pathologies in patients with primary unknown musculoskeletal lesions (MSLs). In total, 13 patients with MSLs underwent dynamic scans (5–10 [phase 1], 10–15 [phase 2], 15–20 [phase 3], 20–25 [phase 4], 25–30 [phase 5], and 30–35 [phase 6] min post-injection of C-11 MET). We statistically compared the maximum standardised uptake values (SUVmax) and corresponding retention index for dynamic scans (RI-SUV) for five benign MSLs (BMSLs), five primary malignant musculoskeletal tumours (PMMSTs), four metastatic musculoskeletal tumours (MMSTs), and three malignant lymphoma (ML) cases and explored their diagnostic capacities using receiver operating characteristic (ROC) curve analyses.

Results

SUVmax gradually decreased or remained similar with minimal fluctuations in all BMSL cases and four of five PMMST cases. In contrast, SUVmax increased over time in one case of PMMST and in all cases of MMST and ML. Significant differences were observed in SUVmax for all time phases and RI-SUV between BMSLs and MMSLs, in SUVmax for all time phases between PMMSTs and BMSLs, in SUVmax for all time phases and RI-SUV between non-PMMST-malignant tumours and BMSL, and in RI-SUV between non-PMMST-malignant tumours and PMMST. In ROC analyses, the areas under the curve yielded the highest values at 1.00 for differentiating most intergroup comparisons.

Conclusions

Dynamic C-11 MET PET scans have the potential to be good predictors of discriminating MSLs in patients with primary unknown MSLs in clinical practice.

Extra-hepatic sarcoma metastasis surveillance in the liver: is arterial phase imaging necessary?

PURPOSE

To assess the value of arterial phase imaging (ART) in the detection of liver metastases on CT compared to portal venous phase imaging (PV) alone in patients with primary sarcomas.

METHODS

Multiphasic abdominal computed tomography (CT) images of patients with tissue-proven sarcomas were reviewed by five abdominal radiologists in a staggered fashion. Up to three of the largest or most conspicuous liver lesions were characterized on a four-point confidence level for PV independently, followed by PV + ART. Inter-observer reliability was evaluated with kappa statistics. Change in characterization of lesions by the addition of ART was calculated. Follow-up imaging was used to determine if index lesion characterization was valid.

RESULTS

55 of 149 patients had 470 liver lesion characterizations by the five readers with follow-up. Inter-observer agreement was κ = 0.62 on PV and κ = 0.58 on PV + ART. The intra-observer agreement between PV and ART interpretations of the same lesion was κ = 0.93. 426 lesion characterizations were possible on both PV and ART. Only 6 characterizations were changed after the addition of ART; 4 of the 6 changes were incorrect when compared to follow-up. Only 6 lesion characterizations could be made on ART alone (missed by PV), with all the malignant lesions arising from primary leiomyosarcomas. For the lesions seen on PV alone, the sensitivity, specificity, PPV, NPV, and accuracy were 98.8%, 100%, 100%, 99.3%, and 99.6%, respectively. After the addition of ART, they were 98.8%, 98.7%, 97.5%, 99.4%, and 98.7%, respectively.

CONCLUSION

ART adds marginal value to PV for characterization of metastatic liver lesions in patients with primary sarcomas, except possibly in primary leiomyosarcomas.

The Possible Role of PET Imaging Toward Individualized Management of Bone and Soft Tissue Malignancies

This article presents fluorodeoxyglucose PET/computed tomography for the evaluation of soft tissue sarcomas. Its clinical impact is discussed analyzing all the clinical information provided when applied in different phases of the disease. A special paragraph is dedicated to the use of functional imaging for driving the biopsy.

Translational research in diagnosis and management of soft tissue tumours

Finding a soft tissue mass in the superficial regions is a common event in daily clinical practice. Correct management of the diagnostic process is crucial to avoid blunders. Diagnosis is posed by pathology, although both imaging and a better understanding of the cellular and molecular mechanisms play an important a role in the characterization, staging and follow-up of soft tissue masses. Cellular and molecular mechanisms can explain either the development of chemo-resistance and the underlying pre- and post-surgery metastasis formation. These are mandatory to improve prognosis and unveil novel parameters predicting therapeutic response. Imaging mainly involves ultrasound and MR and is fundamental not only in diagnosis but also in the first step of therapy: the biopsy. Novel imaging techniques like Ultrasound Elastosonography, Dynamic Contrast-Enhanced MR imaging (DCE), Diffusion Weighted MR imaging (DWI) and MR Spectroscopy (MRS) are discussed. This paper aims at reviewing and discussing pathological methods and imaging in the diagnosis of soft tissue masses underscoring that the most appropriate treatment depends on advanced molecular and radiological studies.

Applying Advanced Imaging Techniques to a Murine Model of Orthotopic Osteosarcoma

INTRODUCTION

Reliable animal models are required to evaluate novel treatments for osteosarcoma. In this study, the aim was to implement advanced imaging techniques in a murine model of orthotopic osteosarcoma to improve disease modeling and the assessment of primary and metastatic disease.

MATERIALS AND METHODS

Intra-tibial injection of luciferase-tagged OPGR80 murine osteosarcoma cells was performed in Balb/c nude mice. Treatment agent [pigment epithelium-derived factor (PEDF)] was delivered to the peritoneal cavity. Primary tumors and metastases were evaluated by in vivo bioluminescent assays, micro-computed tomography, [(18)F]-Fluoride-PET and [(18)F]-FDG-PET.

RESULTS

[(18)F]-Fluoride-PET was more sensitive than [(18)F]-FDG-PET for detecting early disease. Both [(18)F]-Fluoride-PET and [(18)F]-FDG-PET showed progressive disease in the model, with fourfold and twofold increases in standardized uptake value (p < 0.05) by the study endpoint, respectively. In vivo bioluminescent assay showed that systemically delivered PEDF inhibited growth of primary osteosarcoma.

DISCUSSION

Application of [(18)F]-Fluoride-PET and [(18)F]-FDG-PET to an established murine model of orthotopic osteosarcoma has improved the assessment of disease. The use of targeted imaging should prove beneficial for the evaluation of new approaches to osteosarcoma therapy.

A retrospective study comparing contrast-enhanced computed tomography with 18F-FDG-PET/CT in the early follow-up of patients with retroperitoneal sarcomas

OBJECTIVE

To compare 18-fluorine-labeled 2-deoxy-2-fluoro-D-glucose PET/computed tomography ((18)F-FDG-PET/CT) with contrast enhancement computed tomography (CECT) in the early follow-up of patients who had undergone treatment for primitive retroperitoneal sarcomas (RS).

METHODS

This is a retrospective study on 24 patients who underwent (18)F-FDG-PET/CT and CECT within 2 years after therapy for RS. (18)F-FDG-PET/CT and CECT results were compared with results of histological examination and clinical-instrumental follow-up. We calculated the sensitivity and specificity of CECT and (18)F-FDG-PET/CT for retroperitoneal recurrences and compared them with results of the McNemar test. Negative predictive values (NPVs) and positive predictive values (PPVs) were calculated and the positive percentage agreement and negative percentage agreement were evaluated.

RESULTS

The sensitivity and specificity of (18)F-FDG-PET/CT were 66.7 and 100% and those for CECT were 58.3 and 50%, respectively. For (18)F-FDG-PET/CT, PPV was 100% [95% confidence interval (CI): 67-100%] and NPV was 75% (95% CI: 58-75%); for CECT, PPV was 54% (95% CI: 33-73%) and NPV was 55% (95% CI: 30-78%). Positive percentage agreement and negative percentage agreement were, respectively, 38 and 72% for retroperitoneal lesions, 42.8 and 100% for liposarcomas, 40 and 50% for leiomyosarcomas, 14.2 and 94% for abdominal lymph nodes, and 16.6 and 100% for lung metastasis. Neither technique gave reliable results for liver metastasis.

CONCLUSION

Our data show that (18)F-FDG-PET/CT has a higher overall specificity compared with CECT in identifying areas of recurrence, demonstrating its validity for early whole-body detection of lesions. In our hands (18)F-FDG-PET/CT seems to be a good tool in the early follow-up of patients experiencing recurrence of RS.

Magnetic resonance imaging and thallium-201 scintigraphy for the diagnosis of localized pigmented villonodular synovitis arising from the elbow: A case report and review of the literature

Pigmented villonodular synovitis (PVNS) arising from the elbow joint is extremely rare; only 24 cases have been reported. It is extremely difficult to differentiate PVNS from other soft tissue tumors on the basis of imaging findings alone. Therefore, a biopsy is required for definitive diagnosis. A 20-year-old female reported a mass on her right elbow. Physical examination revealed a tumor measuring 3.0x3.0 cm. Magnetic resonance imaging (MRI) revealed that the signal intensity of the tumor was isointense to muscle on T1-weighted images; however, it was hyper- or isointense to muscle on T2-weighted images. In images obtained by gadolinium-enhanced MRI, the margin of the tumor was well-contrasted. Thallium (Tl)-201 scintigrams revealed an abnormal accumulation in the area of the mass in the early and delayed phases. On the basis of clinical findings, imaging characteristics and incision biopsy results, localized PVNS was diagnosed and marginal excision was performed. We thus identified an extremely rare case of PVNS arising from the elbow joint. When interpreting Tl-201 images for the assessment of bone and soft tissue lesions, it is important to recognize PVNS as a condition that simulates malignant tumors. Furthermore, PVNS should be considered in the differential diagnosis when increased Tl-201 activity is closely related to the joint. MRI aids in the differentiation by demonstrating features of hemosiderin degradation products. These findings are likely to be extremely helpful in the differential diagnosis of bone and soft tissue tumors.

(18) F-fluorodeoxyglucose positron emission tomography/computed tomography for the detection of recurrent bone and soft tissue sarcoma

BACKGROUND

The clinical utility of modern hybrid imaging modalities for detecting recurrent bone or soft tissue sarcoma remains to be determined. In this report, the authors present a clinical study on the diagnostic accuracy and incremental value of integrated (18) F-fluorodeoxyglucose positron emission tomography/computed tomography ((18) F-FDG PET/CT) in patients with a history of sarcoma who have clinically suspected disease recurrence.

METHODS

Forty-three patients who had a history of bone or soft tissue sarcoma and had documented complete remission underwent (18) F-FDG PET/CT. Image analysis was performed independently for (18) F-FDG PET (n = 43) and for contrast-enhanced spiral CT (CE-CT) (n = 30) by 2 separate readers, whereas combined (18) F-FDG PET/CT (n = 43) images were analyzed in consensus by both readers. Imaging findings were rated on a 5-point scale and finally were reported as malignant, benign, or equivocal. Imaging findings were validated either by histopathology (n = 24) or by clinical follow-up (n = 19).

RESULTS

(18) F-FDG PET/CT had greater sensitivity and specificity compared with CE-CT alone (94% and 92% vs 78% and 67%, respectively), resulting in significantly greater accuracy (93% vs 73%; P = .03). (18) F-FDG PET/CT was particularly superior regarding detection of local recurrence or soft tissue lesions (sensitivity and specificity: 83% and 100% vs 50% and 100%, respectively) or bone metastases (100% and 100% vs 85% and 88%, respectively).

CONCLUSIONS

(18) F-FDG PET/CT had greater diagnostic accuracy in the detection of recurrent bone or soft tissue sarcoma compared with CE-CT alone. The detection of local recurrence was the most evident advantage of (18) F-FDG PET/CT over CE-CT. Cancer 2013. © 2012 American Cancer Society.

Thallium-201 scintigraphy is an effective diagnostic modality to distinguish malignant from benign soft-tissue tumors

BACKGROUND

The aim of this study is to evaluate whether thallium-201 (201-Tl) scintigraphy can differentiate malignant from benign soft-tissue tumors.

METHODS

Between April 1995 and December 2005, 192 patients with soft-tissue tumors (85 malignant and 107 benign) underwent 201-Tl scintigraphy before treatment. Isotope uptake was used as a proxy for tumor-to-background ratio (TBR). The accuracy of TBR on early and delayed imaging was evaluated using the Mann-Whitney U and χ(2) tests.

RESULTS

There was a statistically significant difference in mean TBR on early and delayed imaging of malignant and benign soft-tissue tumors (124% ± 109% vs. 22% ± 42%, and 82% ± 83% vs. 12% ± 25%, P < 0.0001). A TBR cutoff of 20% indicated the probability of malignancy on early and delayed imaging (82% sensitivity and 77% specificity; 82% sensitivity and 84% specificity, P < 0.0001). Well-differentiated liposarcomas showed low isotope accumulation, while pigmented villonodular synovitis and giant cell tumors of the tendon sheath showed high isotope accumulation.

CONCLUSIONS

Thallium-201 scintigraphy can distinguish malignant from benign tumors with relatively high accuracy. With the exception of low grade liposarcomas and locally aggressive benign tumors, 201-Tl scintigraphy may be an effective diagnostic modality to differentiate malignant from benign soft-tissue tumors.

The role of imaging for translational research in bone tumors

Sarcomas are a heterogeneous group of rare connective tissue tumors, representing 1% of adult and 15% of childhood cancers for which biological and pathological information is still incomplete. In bone tumors patients with metastatic disease at onset, those who relapse and those with post-surgical secondary lesions still have a dismal outcome because of poor response to current therapies. Different molecular biology approaches have identified activated cell signalling pathways or specific molecular endpoints that may be considered potential drug targets or markers useful for diagnosis/prognosis in musculoskeletal pathology. Recently, advances in the field of molecular imaging allow visualization of cell and metabolic functions with the use of targets that include cell membrane receptors, enzymes of intracellular transport. Moreover advanced non-invasive newer imaging techniques like 18-FDG PET, quantitative dynamic-contrast MR imaging, diffusion weighted imaging have all shown a potential in distinguish malignant from benign lesions, in revealing the efficacy of therapy in tumors, the onset of recurrence and a good reliability in reckoning the percentage of necrosis in Ewing sarcoma and osteosarcoma. Thus, in vivo detection of imaging cancer biomarkers may be useful to better characterize those complex pathologic processes, such as apoptosis, proliferation and angiogenesis that determine tumor aggressiveness, providing not only complementary information of prognostic metabolic indicators, but also data in real-time on the efficacy of the treatment through the modulation of the cell metabolism.

Clinical applications of positron emission tomography in sarcoma management

Positron emission tomography (PET) with the fluorine-18-labeled glucose analog FDG is a technique that noninvasively visualizes glucose metabolism in the human body. In oncology, the addition of FDG-PET to the conventional anatomical imaging techniques provides very useful clinical information in diagnosis, staging, treatment response monitoring and follow-up. In the heterogeneous group of patients with sarcoma, FDG-PET has been shown to be of great value in improving patient care. In this article we will discuss the current role of FDG-PET in the management of patients with sarcoma and its value in assessing tumor grade, guiding biopsy, staging, monitoring treatment response, restaging and prognostication. Our future expectation is that the value of PET will only augment owing to the implementation of FDG-PET in clinical guidelines, the increasing availability worldwide, and the development of new tracers and new hybrid imaging techniques.

(18)F-FDG PET in sarcoma treatment response imaging

Sarcomas are a biologically complex group of diseases that exhibit variable responses to single or combination therapy. (18)F-FDG PET imaging contributes to sarcoma treatment response assessment as an objective semiquantitative biomarker of response. In this review, background and experience in (18)F-FDG PET as a biomarker that successfully identifies tumor response is assessed.

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.

Contemporary imaging in sarcoma

Sarcomas are a heterogeneous group of >50 subtypes of neoplasm. It is imperative to obtain appropriate imaging of these tumors in order to adequately assess, characterize, and stage bone and soft tissue sarcomas. Anatomic imaging such as radiographs, computed tomography, and magnetic resonance imaging (MRI) remain the foundation for both biopsy planning and postoperative evaluation of these neoplasms. However, anatomic imaging may not be entirely accurate in the evaluation of treatment response. Newer techniques, such (18)F-fluorodeoxyglucose positron emission tomography, are being used to evaluate distant metastases. Newer radiopharmaceuticals, such as (18)F-fluorodeoxythymidine, are being developed to assist in the differentiation between benign and low-grade malignant neoplasms. Newer functional imaging techniques, such as dynamic contrast-enhanced MRI and diffusion-weighted imaging, among others, are being developed to evaluate treatment response.

Promises and challenges of positron emission tomography for assessment of sarcoma in daily clinical practice

A correct histological diagnosis, careful staging and detection of tumour response to treatment are all crucial in the management of sarcomas. Imaging is important in all of these stages. Sarcomas have distinct biological and treatment-related features posing challenges for imaging. For example, size measurements may not adequately reflect response rates. Techniques which can measure tissue function rather than generate merely anatomical data such as positron emission tomography (PET) are rapidly gaining interest. We discuss the importance of imaging in different stages of patient management, emphasising the unique characteristics of sarcoma. Furthermore, we discuss the potential of PET for the various indications, focussing on therapy evaluation.

Sarcoma

Sarcomas comprise a heterogeneous group of mesenchymal neoplasms. They can be grouped into 2 general categories, soft tissue sarcoma and primary bone sarcoma, which have different staging and treatment approaches. This review includes a discussion of both soft tissue sarcomas (malignant fibrous histiocytoma, liposarcoma, leiomyosarcoma, synovial sarcoma, dermatofibrosarcoma protuberans, angiosarcoma, Kaposi sarcoma, gastrointestinal stromal tumor, aggressive fibromatosis or desmoid tumor, rhabdomyosarcoma, and primary alveolar soft-part sarcoma) and primary bone sarcomas (osteosarcoma, Ewing sarcoma, giant cell tumor, and chondrosarcoma). The 3 most important prognostic variables are grade, size, and location of the primary tumor. The approach to a patient with a sarcoma begins with a biopsy that obtains adequate tissue for diagnosis without interfering with subsequent optimal definitive surgery. Subsequent treatment depends on the specific type of sarcoma. Because sarcomas are relatively uncommon yet comprise a wide variety of different entities, evaluation by oncology teams who have expertise in the field is recommended. Treatment and follow-up guidelines have been published by the National Comprehensive Cancer Network (www.nccn.org).

Clinical applications of molecular imaging in sarcoma evaluation

A wide range of molecular imaging techniques are available that can provide complementary information to conventional, anatomical imaging for the evaluation of known or suspected bone and soft tissue sarcomas. In particular, positron emission tomography (PET), particularly in the form of hybrid PET/CT technology, offers many potential advantages over current imaging approaches by delineating not only the extent of disease but also the biological heterogeneity that can exist both between and within sarcomas. This review discusses the clinical situations where nuclear medicine techniques can aid in the management of patients with sarcoma. These include biopsy guidance, whole body staging, therapeutic response assessment and evaluation of residual mass lesions after treatment.