Correlation Between Glycolytic Phenotype and Tumor Grade in Soft-Tissue Sarcomas by 18F-FDG PET

Tumor glycolytic phenotyping can be accomplished with F-18-FDG PET. Tumor F-18-FDG uptake correlates with tumor grade in several cancers. However, the role of F-18-FDG PET for the grading of soft-tissue sarcomas (STSs) warrants further research. Methods: One hundred two patients (48 men and 54 women; mean age +/- SD, 50 +/- 17 y) with 12 STS subtypes underwent F-18-FDG PET/CT before treatment. Tumor F-18-FDG uptake, expressed as maximum standardized uptake value (SUVmax), was compared among subtypes and correlated with histopathologic grade. Two frequently used sarcoma grading systems-the 3-tier system of the French Federation of Cancer Centers Sarcoma Group (Federation Nationale des Centres de Lutte Contre le Cancer [FNCLCC]) and a 2-tier system (low grade vs. high grade)-were used. Results: More than 90% of STSs (93/102) exhibited a strong glycolytic phenotype (SUV-max, 2.7-52.2 g/mL). Tumor SUVmax differed significantly among tumor grades (P < 0.001 for the 3- and 2-tier grading systems). The FNCLCC and 2-tier grading systems predicted tumor grade with similar accuracy (area under the curve, 0.83 and 0.85, respectively; P = 0.35). SUVmax differed significantly among histologic subtypes (P = 0.03) in the entire population but not when high-grade STSs were analyzed separately (P = 0.31). Conclusion: The tumor glycolytic phenotype correlated significantly with histologic grade as determined by both the FNCLCC and 2-tier (high vs. low) grading systems. F-18-FDG PET cannot be used to reliably distinguish among grade 2 and 3 STSs (by FNCLCC) and the various subtypes.