The role of preoperative 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in retroperitoneal sarcoma

Abstract 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan was used to predict pathologic grade based on the maximum standardized uptake value (SUVmax) in soft tissue sarcoma and bone sarcoma. In retroperitoneal sarcoma (RPS), the effectiveness of PET scan was not well known. This study is designed to investigate the association of SUVmax with histopathologic grade and usefulness of 18 F-FDG PET/CT scan preoperatively. Patients undergoing primary surgery for retroperitoneal sarcoma with preoperative 18F-FDG PET/CT imaging were investigated between January 2001 and February 2020 at Samsung Medical Center. The relationship between SUVmax and histologic features was assessed. The association of SUVmax with overall survival (OS), local recurrence (LR), and distant metastasis (DM) was studied. Of the total 129 patients, the most common histologic subtypes were liposarcoma (LPS, 68.2%) and leiomyosarcoma (LMS,15.5%). The median value of SUVmax was 4.5 (range, 1- 29). The value of SUVmax was correlated with higher tumor grade (p < 0.001, Spearman coefficient 0.627) and mitosis (p < 0.001, Spearman coefficient 0.564) and showed a higher value in LMS (12.04±6.73) than in dedifferentiated liposarcoma (DDLPS, 6.32±4.97, p = 0.0054). The optimal threshold to distinguish high tumor grade was 4.8. High SUVmax group based on the above threshold showed poor prognosis in OS, LR, and DM (p < 0.001). SUVmax was correlated with pathologic parameters (tumor grade, mitosis) in RPS and was higher in the LMS group than DDLPS group. In addition, prognosis (OS, LR, DM) was poor at high SUVmax values (p < 0.001). The value of SUVmax 4.8 is the optimal threshold to rule out high-grade tumors and predict prognosis.