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Determining Glucose Metabolism Kinetics Using 18F-FDG Micro-PET/CT
Published on: May 2, 2017
18F-FDG PET-CT versus MRI for detection of skeletal metastasis in Ewing sarcoma
S E Bosma1, D Vriens2, H Gelderblom3
1Department of Orthopedics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands. s.e.bosma@lumc.nl.
Objective:
To determine the level of discrepancy between magnetic resonance imaging (MRI) and 18F-FDG PET-CT in detecting osseous metastases in patients with Ewing sarcoma.
Methods:
Twenty patients with histopathologically confirmed Ewing sarcoma between 2000 and 2017 who underwent 18F-FDG PET-CT and MRI within a 4-week range were included. Each imaging modality was evaluated by a separate observer. Reference diagnosis of each lesion was based on histopathology or consensus of an expert panel using all available data, including at least 6 months' follow-up. Sensitivity, specificity, and predictive values were determined. Osseous lesions were analyzed on a patient and a lesion basis. Factors possibly related to false-negative findings were evaluated using Pearson's Chi-squared or Fisher's exact test.
Results:
A total of 112 osseous lesions were diagnosed in 13 patients, 107 malignant and 5 benign. Seven patients showed no metastases on either 18F-FDG PET-CT or MRI. Forty-one skeletal metastases (39%) detected with MRI did not show increased 18F-FDG uptake on 18F-FDG PET-CT (false-negative). Lesion-based sensitivities and specificities were 62% (95%CI 52-71%) and 100% (48-100%) for 18F-FDG PET-CT; and 99% (97-100%) and 100% (48-100%) for MRI respectively. Bone lesions were more likely to be false-negative on 18F-FDG PET-CT if hematopoietic bone marrow extension was widespread and active (p = 0.001), during or after (neo)-adjuvant treatment (p = 0.001) or when the lesion was smaller than 10 mm (p < 0.001).
Conclusion:
Although no definite conclusions can be drawn from this small retrospective study, it shows that caution is needed when using 18F-FDG PET-CT for diagnosing skeletal metastases in Ewing sarcoma. Poor contrast between metastases and active hematopoietic bone marrow, chemotherapeutic treatment, and/or small size significantly decrease the diagnostic yield of 18F-FDG PET-CT, but not of MRI.
Insights
Magnetic resonance imaging (MRI) is more reliable than 18F-FDG PET-CT for detecting bone metastases in Ewing sarcoma patients. Factors like active bone marrow, chemotherapy, and small lesion size reduce 18F-FDG PET-CT accuracy.
Area of Science:
- Oncology
- Radiology
- Medical Imaging
Background:
- Ewing sarcoma is a rare bone cancer primarily affecting children and young adults.
- Accurate detection of osseous metastases is crucial for staging and treatment planning in Ewing sarcoma.
- Both magnetic resonance imaging (MRI) and 18F-FDG PET-CT are used for detecting metastases, but their comparative efficacy is debated.
Purpose of the Study:
- To compare the diagnostic accuracy of MRI and 18F-FDG PET-CT in identifying bone metastases in patients with Ewing sarcoma.
- To determine the extent of discrepancy between these two imaging modalities in detecting osseous lesions.
Main Methods:
- A retrospective study included 20 patients with confirmed Ewing sarcoma who underwent both MRI and 18F-FDG PET-CT within a 4-week interval.
- Lesions were evaluated by separate observers for each imaging modality.
- Reference diagnosis was established through histopathology or expert consensus with at least 6 months of follow-up.
- Sensitivity, specificity, and predictive values were calculated on a patient and lesion basis.
Main Results:
- Of 112 osseous lesions identified, 107 were malignant.
- MRI detected 41 lesions (39%) that showed no increased 18F-FDG uptake on PET-CT (false negatives for PET-CT).
- Lesion-based sensitivity and specificity were 62% and 100% for 18F-FDG PET-CT, versus 99% and 100% for MRI.
- False-negative findings on 18F-FDG PET-CT were associated with widespread active bone marrow, prior/current chemotherapy, and lesions smaller than 10 mm.
Conclusions:
- MRI demonstrates higher sensitivity and specificity for detecting osseous metastases in Ewing sarcoma compared to 18F-FDG PET-CT.
- 18F-FDG PET-CT's diagnostic yield is significantly reduced by factors such as poor contrast with active bone marrow, neoadjuvant/adjuvant treatment, and small lesion size.
- Caution is advised when relying solely on 18F-FDG PET-CT for diagnosing skeletal metastases in Ewing sarcoma, while MRI remains a robust tool.
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