Purpose or Case Report: This study explored whether background 18F-FDG uptake differs between pediatric sarcoma cases (patients who underwent PET-CT as part of their clinical evaluation, at diagnosis, or during treatment) and non-oncologic NF-1 controls, reflecting possible systemic metabolic changes in cases that might distinguish tissues in this group from corresponding tissues in controls.
Methods & Materials: 46 pediatric patients were included: 38 with sarcoma, 19 (50%) females, and 8 with NF1, 3 (38%) females. The median age was 10 years (range: 0.3–17) for cases and 11.5 years (range: 7–17) for controls. Two independent readers measured maximum and mean standardized uptake values (SUVmax and SUVmean, respectively) within predefined background regions-of-interest (ROI) on PET-CT scans including: liver, aortic blood pool, lung, sternocleidomastoid muscle, vastus lateralis muscle, and pancreas. Inter-reader reliability was assessed using intraclass correlation coefficients (ICCs). Differences in background SUVs between cases and controls were analyzed after testing for normality, with and without applying Bonferroni correction for multiple comparisons.
Results: There was good to excellent inter-reader agreement across most ROIs (ICC 0.83–0.93; excellent > 0.90, good 0.75–0.90), indicating high measurement reproducibility. The ROIs representing muscles (Sternocleidomastoid and vastus lateralis) demonstrated moderate agreement (ICC 0.50–0.75). Before Bonferroni correction, borderline differences were noted between cases and the controls in a few ROIs. Specifically, measurements in the superior pole of the right lung demonstrated differences at alpha level <0.05 in both SUVmax (p=0.044) and SUVmean (p=0.037), while measurements in pancreas showed a difference in SUVmax (p=0.038). However, none of these findings remained statistically significant after Bonferroni correction.
Conclusions: Borderline differences in background 18F-FDG uptake were observed between pediatric patients with sarcoma (cases) and NF1 (controls) before Bonferroni adjustment, pointing to potential differential metabolic activity of body tissues in patients with active sarcoma compared with non-cancer patients. Although these findings require confirmation in larger cohorts, this study introduces the concept that background metabolic activity on PET/CT may carry potential for future cancer risk prediction, offering a new perspective for understanding systemic metabolic alterations associated with malignancy.