Diagnostic and Clinical Impact of 18F-FDG PET/CT in Staging and Restaging Soft-Tissue Sarcomas of the Extremities and Trunk: Mono-Institutional Retrospective Study of a Sarcoma Referral Center

Giant Myxofibrosarcoma in the Lower Limb: An Overview of Diagnostic and Clinical Management

Myxofibrosarcoma (MFS), an aggressive soft tissue sarcoma, is one of the undifferentiated pleomorphic sarcomas; it has a low incidence, affecting people in the sixth to eighth decades of life. It usually involves the extremities and is painless with a slow-growing pattern. Based on the case of a 52-year-old female patient who presented with a painful, massive, rapid-growing, ulcerated tumor of the anterior surface of the left thigh, we performed a literature review regarding the current standard of care for patients with MFS. Computed tomography examination, followed by magnetic resonance imaging and surgical biopsy with histopathological examination, confirmed the diagnosis and the presence of lung and inguinal lymph node metastases. Due to the rapid-growing pattern and the local aggressiveness, our tumor board team recommended emergency excisional surgery, with subsequent reconstructive procedures followed by referral to an oncological center. This review emphasizes the importance of proper and rapid diagnosis, followed by multidisciplinary management, for MFS cases with atypical presentation and distal metastases to improve overall outcomes.

Molecular Imaging in Soft-tissue Sarcoma: Evolving Role of FDG PET

Soft tissue sarcomas are a rare and heterogenous group of tumors that account for 2% of all cancer-related deaths. Molecular imaging with FDG PET can offer valuable metabolic information to help inform clinical management of soft tissue sarcomas that is unique and complementary to conventional diagnostic imaging techniques. FDG PET imaging often correlates with tumor grade, can help guide biopsy, and frequently detects additional sites of disease compared to conventional imaging in patients being considered for definitive or salvage therapy. Traditional size-based evaluation of treatment response is often inadequate in soft tissue sarcoma and changes in metabolic activity can add significant value to interim and end of treatment imaging for high-grade sarcomas. FDG PET can be used for detection of recurrence or malignant transformation and thus play a vital role in surveillance. This article reviews the evolving role of FDG PET in initial diagnosis, staging, treatment response assessment, and restaging. Further studies on the use of FDG PET in soft sarcoma are needed, particularly for rare histopathologic subtypes.

Can FDG-PET assess the response to chemotherapy and predict tissue necrosis in osteosarcoma and Ewing sarcoma?

INTRODUCTION

Osteosarcoma (OS) and Ewing sarcoma (ES) represent the pediatric population's most common malignant bone tumors. 18-Fluorodeoxyglucose positron emission tomography has been shown to be effective in both the diagnostic and staging phases of cancer treatment. In recent years, some studies have also explored the possibility that FDG-PET could have a prognostic role.

Positron Emission Tomography/Computed Tomography Transformation of Oncology: Musculoskeletal Cancers

The past 25 years have seen significant growth in the role of positron emission tomography/computed tomography (PET/CT) in musculoskeletal oncology. Substantiative advances in technical capability and image quality have been paralleled by increasingly widespread clinical adoption and implementation. It is now recognized that PET/CT is useful in diagnosis, staging, prognostication, response assessment, and surveillance of bone and soft tissue sarcomas, often providing critical information in addition to conventional imaging assessment. As individualized, precision medicine continues to evolve for patients with sarcoma, PET/CT is uniquely positioned to offer additional insight into the biology and management of these tumors.

Diagnostic Accuracy of 68Ga-FAPI Versus 18F-FDG PET in Patients with Various Malignancies

To assess the diagnostic accuracy of 68Ga-labeled fibroblast activation protein inhibitor (FAPI) and 18F-labeled FDG PET for the detection of various tumors, we performed a head-to-head comparison of both imaging modalities across a range of tumor entities as part of our ongoing 68Ga-FAPI PET observational trial. Methods: The study included 115 patients with 8 tumor entities who received imaging with 68Ga-FAPI for tumor staging or restaging between October 2018 and March 2022. Of those, 103 patients received concomitant imaging with 68Ga-FAPI and 18F-FDG PET and had adequate lesion validation for accuracy analysis. Each scan was evaluated for the detection of primary tumor, lymph nodes, and visceral and bone metastases. True or false positivity and negativity to detected lesions was assigned on the basis of histopathology from biopsies or surgical excision, as well as imaging validation. Results: 68Ga-FAPI PET revealed higher accuracy than 18F-FDG PET in the detection of colorectal cancer (n = 14; per-patient, 85.7% vs. 78.6%; per-region, 95.6% vs. 91.1%) and prostate cancer (n = 22; per-patient, 100% vs. 90.9%; per-region, 96.4% vs. 92.7%). 68Ga-FAPI PET and 18F-FDG PET had comparable per-patient accuracy in detecting breast cancer (n = 16, 100% for both) and head and neck cancers (n = 10, 90% for both modalities). 68Ga-FAPI PET had lower per-patient accuracy than 18F-FDG PET in cancers of the bladder (n = 12, 75% vs. 100%) and kidney (n = 10, 80% vs. 90%), as well as lymphoma (n = 9, 88.9% vs. 100%) and myeloma (n = 10, 80% vs. 90%). Conclusion: 68Ga-FAPI PET demonstrated higher diagnostic accuracy than 18F-FDG PET in the diagnosis of colorectal cancer and prostate cancer, as well as comparable diagnostic performance for cancers of the breast and head and neck. Accuracy and impact on management will be further assessed in an ongoing prospective interventional trial (NCT05160051).

Head to head comparison of 68Ga-DOTA-FAPI-04 vs 18F-FDG PET/CT in the evaluation of primary extrapulmonary tumors in the chest

OBJECTIVE

We conducted a prospective study using 18F-flurodeoxyglucose (18F-FDG) and 68Ga-DOTA-FAPI-04 (fibroblast-activation protein inhibitor, 68Ga-FAPI) PET/CT to diagnose, differentiate, and stage primary extrapulmonary tumors of the thorax.

METHODS

Fifty-four participants were undergoing 18F-FDG and 68Ga-FAPI PET/CT and divided into the benign, intermediate, and malignant based on pathology. The maximum standardized uptake value (SUVmax), the tumor-to-blood pool ratio, and tumor-to-liver ratio were compared for primary tumors, lymph nodes, and metastases between the two modalities by two independent samples t tests. One-way ANOVA was used to compare the uptake of 18F-FDG or 68Ga-FAPI among the three groups.

RESULTS

Fifty-four participants were confirmed to have 71 primary lesions, 56 metastatic lymph nodes, and 43 metastatic lesions. 18F-FDG PET/CT could both effectively distinguish malignant lesions from non-malignant lesions, accuracies of 87.32% (p < 0.001). 68Ga-FAPI PET/CT effectively differentiated benign lesions from the non-benign, accuracy being 91.55% (p < 0.001). The accuracies of 18F-FDG and 68Ga-FAPI for detecting lymph node metastasis were 77.22% (61/79) and 87.34% (69/79) (p = 0.096). The uptake of 68Ga-FAPI in metastatic lymph nodes was significantly higher than that of the nonmetastatic (p < 0.001). The detection rate of 68Ga-FAPI PET/CT for metastatic lesions was significantly higher than that of 18F-FDG, 100% (43/43) vs. 53.49% (23/43) (p < 0.001). Compared with 18F-FDG PET/CT, 68Ga-FAPI PET/CT changed the treatment strategy of 7.4% (4/54) participants.

CONCLUSION

68Ga-FAPI PET/CT is valuable in the diagnosis and differentiation of primary extrapulmonary tumors and superior to 18F-FDG PET/CT for evaluating lymph node and distant metastasis.

CLINICAL RELEVANCE STATEMENT

The application of 68Ga-FAPI PET/CT in primary extrapulmonary chest tumors is valuable, which is reflected in diagnosis, differentiation and exploration of lymph node metastasis and distant metastasis.

KEY POINTS

• 68Ga-FAPI PET/CT is valuable in the diagnosis, differentiation, and staging of primary extrapulmonary tumors. • 68Ga-FAPI PET/CT is superior to 18 F-FDG PET/CT for evaluating lymph node and distant metastasis.

Diagnostic Superiority of Dual-Time Point [18F]FDG PET/CT to Differentiate Malignant from Benign Soft Tissue Tumors

[18F]FDG PET/CT is used in the workup of indeterminate soft tissue tumors (STTs) but lacks accuracy in the detection of malignant STTs. The aim of this study is to evaluate whether dual-time point [18F]FDG PET/CT imaging (DTPI) can be useful in this indication. In this prospective study, [18F]FDG PET/CT imaging was performed 1 h (t1) and 3 h (t2) after injection. Tumor uptake (SUVmax) was calculated at each time point to define a retention index (RI) corresponding to the variation between t1 and t2 (%). Sixty-eight patients were included, representing 20 benign and 48 malignant tumors (including 40 sarcomas). The RI was significantly higher in malignant STTs than in benign STTs (median: +21.8% vs. -2%, p < 0.001). An RI of >14.3% predicted STT malignancy with a specificity (Sp) of 90% and a sensitivity (Se) of 69%. An SUVmaxt1 of >4.5 was less accurate with an Sp of 80% and an Se of 60%. In a subgroup of tumors with at least mild [18F]FDG uptake (SUVmax ≥ 3; n = 46), the RI significantly outperformed the diagnostic accuracy of SUVmax (AUC: 0.88 vs. 0.68, p = 0.01). DTPI identifies malignant STT tumors with high specificity and outperforms the diagnostic accuracy of standard PET/CT.

Biology and Management of High-Grade Myxofibrosarcoma: State of the Art and Future Perspectives

Myxofibrosarcoma (MFS) is one of the most common adult soft tissue sarcomas, typically arising in the extremities. Histologically, MFS is classified into three grades: low, intermediate, and high. Histological grades correlate with distant metastases and tumor-associated mortality. The diagnosis of MFS is challenging due to a lack of well-characterized immunohistochemical markers. High-grade MFS displays highly complex karyotypes with multiple copy number alterations. Recent integrated genomic studies have shown the predominance of somatic copy number aberrations. However, the molecular pathogenesis of high-grade MFS remains poorly understood. The standard treatment for localized MFS is surgical resection. The systemic treatment options for advanced disease are limited. This review provides an updated overview of the clinical and imaging features, pathogenesis, histopathology, and treatment of high-grade MFS.

Differentiating primary from secondary lung cancer with FDG PET/CT and extra-pulmonary tumor grade

OBJECTIVE

Assess feasibility of differentiating primary from secondary lung cancer in patients with a solid solitary malignant pulmonary lesion (SMPL) and a previously resected extrapulmonary tumor.

METHODS

Patients with pathology proven primary or secondary lung cancer from a solitary pulmonary lesion and known histopathology of extrapulmonary tumor were included. Patients with a small pulmonary lesion size, multiple malignant pulmonary nodules or an active infectious/inflammatory process were excluded. Extrapulmonary tumor grade was categorized as low, intermediate and high and was matched to FDG uptake intensity of SMPL, with FDG uptake range (SMPL/Liver SUVmax) of <0.9 for low, 0.91-1.99 for intermediate and >2.0 for high extrapulmonary tumor grade.

RESULTS

Of 274 patients, 62 met the study criteria. 46 are primary and 16 are secondary lung cancer. There are 19 low, 27 intermediate and 16 high grade extrapulmonary tumors. Mean SMPL SUVmax is 8.2 ± 4.5 and SMPL/liver SUVmax is 2.4 ± 1.4. There are 37 cases (60%) with mismatched results (e.g., low FDG SMPL with intermediate or high grade extrapulmonary tumor or vice versa) and 25 matched cases (40%) that are inconclusive (e.g., low FDG with low tumor grade or high FDG with high tumor grade). Of the mismatched cases, we correctly predicted 30 cases (81%) as primary lung cancers.

CONCLUSION

A mismatch between the SMPL SUVmax and the extrapulmonary tumor grade could be used to differentiate a primary lung cancer from a metastasis with reasonable accuracy. Our preliminary results support the hypothesis that FDG uptake intensity of a metastatic pulmonary lesion mirrors the tumor aggressiveness of its extrapulmonary neoplasm of origin.

Molecular imaging of sarcomas with FDG PET

Sarcoma comprises a heterogenous entity of musculoskeletal malignancies arising from a mesenchymal origin. The diagnosis and management of pediatric sarcoma requires a multidisciplinary approach and the use of various imaging modalities including CT, MRI and FDG PET scans. FDG PET/CT (FDG PET), as a metabolic imaging, complements and provides superior diagnostic information as against other imaging modalities alone. Advantages of FDG PET in differentiating malignant sarcomatous lesions from benign lesions, and value in staging and restaging have been noted in several studies. The use of FDG PET in clinical management has increased over the years. The data on prognostication of outcomes or predicting responders to therapy with FDG PET in patients with sarcoma is somewhat limited. This review will focus on the pearls and pitfalls of FDG PET and role of FDG PET in initial extent of disease assessment, treatment response, and surveillance imaging pertaining to osteosarcoma, chondrosarcoma, Ewing's sarcoma, and rhabdomyosarcoma. We also discuss the limitations and unmet needs of FDG PET in the management of patients with sarcoma.

Prognostic Value of Pre-Treatment [18F]FDG PET/CT Texture Analysis in Undifferentiated Soft-Tissue Sarcoma

BACKGROUND

Undifferentiated soft-tissue sarcomas (USTS) are one of the most common sarcoma histotypes in adults. The standard of care is surgical excision plus adjuvant radiotherapy, while the use of perioperative chemotherapy is still controversial. The aim of this study was to investigate the value of pre-treatment [18F]FDG PET/CT conventional metrics and textural features in predicting disease-free survival (DFS) and overall survival (OS) in patients with USTS of the limbs and trunk.

METHODS

[18F]FDG PET/CT scans of 51 consecutive patients with locally advanced USTS were retrospectively evaluated. Conventional and textural PET parameters were analysed and tested as predictive factors for DFS and OS.

RESULTS

During a median follow up of 50.7 months, 23 (45.1%) and 29 (56.9%) patients had death or disease progression, respectively. Univariate analysis revealed a significant association for perioperative treatment, PET volumetric parameters and the textural feature GLCM_correlation with DFS and OS. In multivariate analysis, perioperative treatment and GLCM_correlation were the only independent factors, allowing stratification of the population into three different prognostic classes.

CONCLUSION

GLCM_correlation can identify USTS at high risk of relapse and death, thus helping to optimize the perioperative treatment of patients.

PET-CT in the Evaluation of Neoadjuvant/Adjuvant Treatment Response of Soft-tissue Sarcomas: A Comprehensive Review of the Literature

➢

In soft-tissue sarcomas (STSs), the use of positron emission tomography-computed tomography (PET-CT) through a standardized uptake value reduction rate correlates well with histopathological response to neoadjuvant treatment and survival.

➢

PET-CT has shown a better sensitivity to diagnose systemic involvement compared with magnetic resonance imaging and CT; therefore, it has an important role in detecting recurrent systemic disease. However, delaying the use of PET-CT scan, to differentiate tumor recurrence from benign fluorodeoxyglucose uptake changes after surgical treatment and radiotherapy, is essential.

➢

PET-CT limitations such as difficult differentiation between benign inflammatory and malignant processes, inefficient discrimination between benign soft-tissue tumors and STSs, and low sensitivity when evaluating small pulmonary metastases must be of special consideration.

Efficacy of Pazopanib in the Treatment of Metastatic Malignant Giant Cell Tumor of Soft Tissue: A Case Report

Giant cell tumor of soft tissue (GCT-ST), histologically resembling the GCT of the bone, is a rare tumor. The tumor has been categorized to have low malignancy. Few reports of local recurrence or distant metastasis and the use of chemotherapeutic agents for metastatic GCT-ST exist. Herein, we report the efficacy of pazopanib in a 78-year-old Japanese woman with GCT in the intrinsic back musculature with both post-operative local recurrence and lung metastasis. The patient visited the hospital with a three-month history of a palpable mass in the intrinsic back musculature. Following magnetic resonance imaging, the tumor predominantly exhibited slight hyperintensity on T2-weighted images and intense heterogeneous enhancement on contrast-enhanced T1-weighted images. A percutaneous needle biopsy was performed, and the pathological diagnosis was GCT-ST. The patient underwent surgery, and three months later she presented with not only local recurrence but also multiple lung metastases. The patient was immediately treated with pazopanib 400 mg once daily. One month after initiating treatment, a partial response in the pulmonary lesions was observed, and stable disease (SD) effects lasted for 11 months without severe adverse effects. Therefore, pazopanib treatment for metastatic malignant giant cell tumor of soft tissue achieved reasonable success.

What is the clinical impact of staging and surveillance PET-CT scan findings in patients with bone and soft tissue sarcoma?

BACKGROUND AND OBJECTIVES

Positron emission tomography-computerized tomography (PET-CTs) are becoming increasingly utilized in sarcoma care, workup, and surveillance. This study aimed to describe additional PET-CT findings as well as subsequent workups and changes in the clinical course due to those results.

METHODS

Patient records were retrospectively reviewed, and the additional workups and evaluations triggered by PET-CT findings were qualitatively analyzed to document their results. Additional changes in the clinical course were documented.

RESULTS

A total of 183 bone and soft tissue sarcoma patients underwent PET-CT as part of staging or surveillance. Additional workup was performed in 31.5% (n = 41 of 130) patients who had positive PET-CT findings. Among these, 36.6% (n = 15 of 41) patients had clinically significant findings that altered the clinical course. Overall, 14.8% (n = 27 of 183) experienced a change in the clinical course due to PET-CT.

CONCLUSION

PET-CT often highlights lesions of potential clinical importance. Additional workup, as well as changes in the clinical course, were not infrequent. Future, multi-institutional studies should address the value of PET-CT in sarcoma care.

68Ga-FAPI as a Diagnostic Tool in Sarcoma: Data from the 68Ga-FAPI PET Prospective Observational Trial

Bone and soft-tissue sarcomas express fibroblast activation protein (FAP) on tumor cells and associated fibroblasts. Therefore, FAP is a promising therapeutic and diagnostic target. Novel radiolabeled FAP inhibitors (e.g., 68Ga-FAPI-46) have shown high tumor uptake on PET in sarcoma patients. Here, we report the endpoints of the 68Ga-FAPI PET prospective observational trial. Methods: Forty-seven patients with bone or soft-tissue sarcomas undergoing clinical 68Ga-FAPI PET were eligible for enrollment into the 68Ga-FAPI PET observational trial. Of these patients, 43 also underwent 18F-FDG PET. The primary study endpoint was the association between 68Ga-FAPI PET uptake intensity and histopathologic FAP expression analyzed with Spearman r correlation. Secondary endpoints were detection rate, positive predictive value (PPV), interreader reproducibility, and change in management. Datasets were interpreted by 2 masked readers. Results: The primary endpoint was met, and the association between 68Ga-FAPI PET uptake intensity and histopathologic FAP expression was significant (Spearman r = 0.43; P = 0.03). By histopathologic validation, PPV was 1.00 (95% CI, 0.87-1.00) on a per-patient and 0.97 (95% CI, 0.84-1.00) on a per-region basis. In cases with histopathologic validation, 27 of 28 (96%) confirmed patients and 32 of 34 (94%) confirmed regions were PET-positive, resulting in an SE of 0.96 (95% CI, 0.82-1.00) on a per-patient and 0.94 (95% CI, 0.80-0.99) on a per-region basis. The detection rate on a per-patient basis in 68Ga-FAPI and 18F-FDG PET was 76.6% and 81.4%, respectively. In 8 (18.6%) patients, 68Ga-FAPI PET resulted in an upstaging compared with 18F-FDG PET. 68Ga-FAPI PET readers showed substantial to almost perfect agreement for the defined regions (Fleiss κ: primary κ = 0.78, local nodal κ = 0.54, distant nodal κ = 0.91, lung κ = 0.86, bone κ = 0.69, and other κ = 0.65). Clinical management changed in 13 (30%) patients after 68Ga-FAPI PET. Conclusion: We confirm an association between tumoral 68Ga-FAPI PET uptake intensity and histopathologic FAP expression in sarcoma patients. Further, with masked readings and independent histopathologic validation, 68Ga-FAPI PET had a high PPV and sensitivity for sarcoma staging.

Prognostic Value of Quantitative [18F]FDG-PET Features in Patients with Metastases from Soft Tissue Sarcoma

Background: Prognostic biomarkers are pivotal for adequate treatment decision making. The objective of this study was to determine the added prognostic value of quantitative [¹⁸F]FDG-PET features in patients with metastases from soft tissue sarcoma (STS). Methods: Patients with metastases from STS, detected by (re)staging [¹⁸F]FDG-PET/CT at Leiden University Medical Centre, were retrospectively included. Clinical and histopathological patient characteristics and [¹⁸F]FDG-PET features (SUVmax, SUVpeak, SUVmean, total lesion glycolysis, and metabolic tumor volume) were analyzed as prognostic factors for overall survival using a Cox proportional hazards model and Kaplan–Meier methods. Results: A total of 31 patients were included. SUVmax and SUVpeak were significantly predictive for overall survival (OS) in a univariate analysis (p = 0.004 and p = 0.006, respectively). Hazard ratios (HRs) were 1.16 per unit increase for SUVmax and 1.20 per unit for SUVpeak. SUVmax and SUVpeak remained significant predictors for overall survival after correction for the two strongest predictive clinical characteristics (number of lesions and performance status) in a multivariate analysis (p = 0.02 for both). Median SUVmax and SUVpeak were 5.7 and 4.9 g/mL, respectively. The estimated mean overall survival in patients with SUVmax > 5.7 g/mL was 14 months; otherwise, it was 39 months (p < 0.001). For patients with SUVpeak > 4.9 g/mL, the estimated mean overall survival was 18 months; otherwise, it was 33 months (p = 0.04). Conclusions: In this study, SUVmax and SUVpeak were independent prognostic factors for overall survival in patients with metastases from STS. These results warrant further investigation of metabolic imaging with [¹⁸F]FDG-PET/CT in patients with metastatic STS.

Fluorine-18-fluorodeoxyglucose (FDG) positron emission tomography (PET) computed tomography (CT) for the detection of bone, lung, and lymph node metastases in rhabdomyosarcoma

BACKGROUND

Rhabdomyosarcoma (RMS) is the most common paediatric soft-tissue sarcoma and can emerge throughout the whole body. For patients with newly diagnosed RMS, prognosis for survival depends on multiple factors such as histology, tumour site, and extent of the disease. Patients with metastatic disease at diagnosis have impaired prognosis compared to those with localised disease. Appropriate staging at diagnosis therefore plays an important role in choosing the right treatment regimen for an individual patient. Fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) is a functional molecular imaging technique that uses the increased glycolysis of cancer cells to visualise both structural information and metabolic activity. 18F-FDG-PET combined with computed tomography (CT) could help to accurately stage the extent of disease in patients with newly diagnosed RMS. In this review we aimed to evaluate whether 18F-FDG-PET could replace other imaging modalities for the staging of distant metastases in RMS.

OBJECTIVES

To determine the diagnostic accuracy of 18F-FDG-PET/CT imaging for the detection of bone, lung, and lymph node metastases in RMS patients at first diagnosis.

SEARCH METHODS

We searched MEDLINE in PubMed (from 1966 to 23 December 2020) and Embase in Ovid (from 1980 to 23 December 2020) for potentially relevant studies. We also checked the reference lists of relevant studies and review articles; scanned conference proceedings; and contacted the authors of included studies and other experts in the field of RMS for information about any ongoing or unpublished studies. We did not impose any language restrictions.

SELECTION CRITERIA

We included cross-sectional studies involving patients with newly diagnosed proven RMS, either prospective or retrospective, if they reported the diagnostic accuracy of 18F-FDG-PET/CT in diagnosing lymph node involvement or bone metastases or lung metastases or a combination of these metastases. We included studies that compared the results of the 18F-FDG-PET/CT imaging with those of histology or with evaluation by a multidisciplinary tumour board as reference standard.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, data extraction, and methodological quality assessement according to Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2). We analysed data for the three outcomes (nodal involvement and lung and bone metastases) separately. We used data from the 2 × 2 tables (consisting of true positives, false positives, true negatives, and false negatives) to calculate sensitivity and specificity in each study and corresponding 95% confidence intervals. We did not consider a formal meta-analysis to be relevant because of the small number of studies and substantial heterogeneity between studies.

MAIN RESULTS

Two studies met our inclusion criteria. The diagnostic accuracy of 18F-FDG-PET/CT was reported in both studies, which included a total of 36 participants. We considered both studies to be at high risk of bias for the domain reference standard. We considered one study to be at high risk of bias for the domain index test and flow and timing. Sensitivity and specificity of 18F-FDG-PET/CT for the detection of bone metastases was 100% in both studies (95% confidence interval (CI) for sensitivity was 29% to 100% in study one and 40% to 100% in study two; 95% CI for specificity was 83% to 100% in study one and 66% to 100% in study two). The reported sensitivity of 18F-FDG-PET/CT for the detection of lung metastases was not calculated since only two participants in study two showed lung metastases, of which one was detected by 18F-FDG-PET/CT. Reported specificity was 96% in study one (95% CI 78% to 100%) and 100% (95% CI 72% to 100%) in study two. The reported sensitivity for the detection of nodal involvement was 100% (95% CI 63% to 100% in study one and 40% to 100% in study two); the reported specificity was 100% (95% CI 78% to 100%) in study one and 89% (95% CI 52% to 100%) in study two.

AUTHORS' CONCLUSIONS

The diagnostic accuracy of 18F-FDG-PET/CT for the detection of bone, lung, and lymph node metastases was reported in only two studies including a total of only 36 participants with newly diagnosed RMS. Because of the small number of studies (and participants), there is currently insufficient evidence to reliably determine the diagnostic accuracy of 18F-FDG-PET/CT in the detection of distant metastases. Larger series evaluating the diagnostic accuracy of 18F-FDG-PET/CT for the detection of metastases in patients with RMS are necessary.

Usefulness of 18f-FDG PET-CT in Staging, Restaging, and Response Assessment in Pediatric Rhabdomyosarcoma

Rhabdomyosarcoma is the most common soft-tissue sarcoma of childhood. Despite clinical advances, subsets of these patients continue to suffer high morbidity and mortality rates associated with their disease. Following the European guidelines for ¹⁸F-FDG PET and PET-CT imaging in pediatric oncology, the routine use of ¹⁸F-FDG PET-CT may be useful for patients affected by rhabdomyosarcoma, in staging, in the evaluation of response to therapy, and for restaging/detection of relapse. The European Pediatric Protocols are very old, and for staging and restaging, they recommend only radionuclide bone scan. The ¹⁸F-FDG PET-CT exam is listed as an optional investigation prescribed according to local availability and local protocols in the investigations panel required at the end of the treatment. We present two cases highlighting the usefulness of ¹⁸F-FDG PET-CT in managing pediatric patients affected by rhabdomyosarcoma, providing some bibliographic references.