Abstract
ObjectiveTo determine the level of discrepancy between magnetic resonance imaging (MRI) and 18F-FDG PET-CT in detecting osseous metastases in patients with Ewing sarcoma.MethodsTwenty 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.ResultsA 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).ConclusionAlthough 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.
Highlights
IntroductionEwing sarcoma is an aggressive primary bone sarcoma, predominantly affecting children and young adults [1, Department of Orthopedics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands
Ewing sarcoma is an aggressive primary bone sarcoma, predominantly affecting children and young adults [1, Department of Orthopedics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The NetherlandsDepartment of Radiology, Leiden University Medical Center, Leiden, The NetherlandsDepartment of Medical Oncology, Leiden University Medical Center, Leiden, The Netherlands2]
In 7 of the 20 patients 18F-FDG PET-computerized tomography (CT) and magnetic resonance imaging (MRI) were both negative for the presence of osseous lesions
Summary
Ewing sarcoma is an aggressive primary bone sarcoma, predominantly affecting children and young adults [1, Department of Orthopedics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands. At the time of diagnosis, 20–25% of the patients present with pulmonary (70–80%) and/or osseous (40–50%) metastases. A multimodal approach to treatment drastically improved survival. Principles of treatment consist of neo-adjuvant chemotherapy followed by local control of the primary tumor, by surgery, radiotherapy or both, and adjuvant chemotherapy [2, 4]. Detection of all metastatic lesions in patients with oligometastatic disease has become relevant, as a curative rather than a palliative treatment objective aimed at achieving local control at these sites has been reported to improve clinical outcome [6]
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