Evaluation of soft tissue lesions with 18F-FDG PET/CT - A prospective trial

Objectives The purpose of this study was to evaluate the usefulness of FDGPET/CT in differentiating benign from malignant solid soft tissue lesions.

Methods Patients with non-fat solid lesions of the upper or lower limbs or abdominal wall detected by MRI were submitted to FDGPET/CT. Patients were required to fast for 6 hours prior to injection of 7.7 MBq/kg of 18F-FDG and whole-body images were acquired on a PET/CT Biograph (Siemens®) after 60 minutes. The SUVmax cutoff was determined to differentiate malignant from benign tumors. Regardless of the FDGPET/CT results all patients underwent ultrasound guided Tru-Cut needle biopsy or excisional biopsy and surgery.

Results MRI was performed in 54 patients. Six patients were excluded because of purely lipomatose lesions. FDGPET/CT was performed in the remaining 48 patients. Histopathology revealed 31 (64.6%) benign and 17 (35.4%) malignant soft tissue lesions. A significant difference was observed in the SUVmax values among benign and malignant soft tissue lesions (p < 0.001; Mann-Whitney U). The SUVmax value cutoff of 3.0 differentiated malignant from benign lesions with 100% sensitivity, 80.6% specificity, 87.5% accuracy, 73.9% PPV and 100% NPV.

Conclusions FDGPET/CT seems to be able to differentiate benign from malignant soft tissue lesions with good accuracy and very high NPV. Incorporating FDGPET/CT into the diagnostic algorithm of these patients may avoid inadequate resections and unnecessary biopsies.

Research Support FAPESP