Differentiation of benign fluid collections from soft-tissue sarcomas on FDG-PET/CT

Objective: To assess the diagnostic performance of ¹⁸F-FDG PET-CT in differentiating soft tissue sarcomas (STSs) from benign fluid collections (BFs). Materials and methods: Four readers independently reviewed 100 lesions on ¹⁸F-FDG PET-CT and subjectively classified each lesion as an STS or BF and scored the spatial pattern of ¹⁸F-FDG avidity (SP) of each on a 4-point ordered scale (thin, moderate, thick, solid). Results: Subjective assessment by readers allowed sensitive (91%-98%) differentiation of STSs from BFs, with lower specificity (59%-91%). The STSs had significantly higher SUV_max (median 10.7, range: 2.0-33.7) than BFs (median 2.8, range: 1.1-12.3). Reader agreement in assessment of SP had average ? = 0.61 (range 0.46-0.70). Classification of thick or solid SP as STS yielded an inter-reader averaged sensitivity and specificity of 69% and 98%, respectively. The presence of thick or solid SP resulted in 14.1-fold increase in partial odds of STS. Each unit increase in SUV_max resulted in 1.35-fold increase in partial odds of STS. The receiver operating characteristic (ROC) curves and 95% intervals for SUV_max alone and SUV_max + SP overlapped. The average subjective assessments for the four readers and estimated performance of using SP alone were both contained within the 95% intervals of the two ROC curves. Conclusions: ¹⁸F-FDG PET-CT is a sensitive modality for differentiating STSs from BFs. SUV_max and SP are significantly associated with STS. Classification schemes based upon SUV_max alone or augmented with SP can be useful for distinguishing STS from BF.