Abstract
1274
Background: Primary cardiac tumors are extremely rare entities, which present a great diagnostic challenge for physicians and radiologists in clinical practice. Although benign primary cardiac tumors with no 18F-FDG uptake are easier to diagnose by 18F-FDG PET/CT, benign tumors with slightly increased uptake are not uncommon, which makes differential diagnosis difficult. Therefore, the purpose of this study was to evaluate the differential diagnostic value of intensity- and volume-based parameters of 18F-FDG PET/CT in primary cardiac tumors with increased 18F-FDG uptake.
Methods: We retrospectively reviewed the medical records of patients with histopathologically confirmed primary cardiac tumors, who underwent preoperative 18F-FDG PET/CT from January 2009 to October 2018. The tumor with increased 18F-FDG uptake in PET imaging was defined as tumor-background-ratio higher than 1 (TBR > 1), and such patients were selected. TBR was calculated by dividing the SUVmax of the tumors by the SUVmax of the root of ascending aorta. Intensity- and volume-based parameters were analyzed. Intensity-based parameters included SUVmax, SUVmean, lean body mass corrected SUVmax (SULmax), glucose-corrected SUVmax (SUVmax-glucose), and TBR. SUVmax-glucose was calculated as SUVmax × blood glucose level / 100. Volume-based parameters included metabolic tumor volume (MTV) and total lesion glycolysis (TLG). MTV was measured with 40% of SUVmax as the threshold for iso-activity contour, and TLG was calculated as the MTV multiplied by the SUVmean of the tumor. All parameters of benign and malignant tumors were assessed using Two-Sample T-test or Mann-Whitney U-test. Receiver operating characteristic (ROC) analysis was performed to determine the area under the ROC curve (AUC) for the above intensity- and volume-based parameters.
Results: A total of 30 patients (mean ± SD: 39.3 ±15.9 years) with 30 tumors (13 benign and 17 malignant) were detected and enrolled (Table 1). All tumors had a TBR more than 1.2 (median: 2.2, range: 1.2-11.30). There were no differences between benign and malignant tumors in baseline characteristics, such as gender, age, glucose level, and injected tracer dose (Figure 1). There were significant differences in intensity-based parameters and TLG between benign and malignant tumors (Figure 1). Intensity-based parameters showed higher AUCs than volume-based parameters (TLG) in primary cardiac tumors with TBR >1 (Figure 2A). SULmax showed the highest AUC of 0.932 among the intensity-based parameters and the cutoff was 4.1 (Figure 2B).
Conclusions: This study revealed that in primary cardiac tumors with increased 18F-FDG uptake, SULmax, as a powerful complement to SUVmax, may be better used to distinguish benign and malignant tumors, while MTV and TLG seem to have a low differential diagnostic value, which still needs to be further investigated with larger sample sizes.