The prognostic value of 18F-FDG PET/CT in postoperative recurrence of retroperitoneal liposarcoma: a single center retrospective study

Purpose: Recurrence is the main cause of tumor-related death of retroperitoneal liposarcoma (RPLPS). Different recurrence pattern was determined by variant subtype of retroperitoneal liposarcoma which displayed diverse presentations on 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography/computed tomography (PET/CT). This study aims to analyze the characteristics of different histologic subtypes of RPLPS on 18F-FDG PET/CT and their associations with recurrence and prognosis.Methods: Clinical-pathological information, 18F-FDG PET/CT, recurrence and progression free survivals (PFS) of 83 patients with RPLPS were collected. Maximum, and peak standardized uptake value (SUVmax and SUVpeak, respectively) and mean CT value (CTmean) of tumors were measured; their correlations with histologic subtype were analyzed. The predictability of SUVmax and CTmean for histologic subtype was evaluated using the receiver operating characteristics (ROC) curve analysis. ROC curve was also performed to analyze the predictive value of SUVmax and peak SUV (SUVpeak) for recurrence. The Kaplan-Meier analysis was performed to analyze whether SUVmax and SUVpeak were risk factors for recurrence. Results: Regarding the histology, 30.1% patients were well-differentiated liposarcoma (WDLPS), 56.6% patients were dedifferentiated liposarcoma (DDLPS), 12.0% patients were myxoid/round cell liposarcoma(MLPS), and 1.2% patients were pleomorphic liposarcoma (PMLPS). SUVmax of DDLPS were significantly higher than those of WDLPS (P < 0.001) and MLPS(P = 0.001). CTmean of WDLPS was significantly lower than those of MLPS (P = 0.001) and DDLPS (P < 0.001). ROC curve suggested 5.1 as an approximate cutoff value of SUVmax for distinguishing DDLPS from non-DDLPS (sensitivity = 76.8%, specificity = 88.0%), and 12.3Hu as cutoff value of CTmean for distinguishing WDLPS from non-WDLPS (sensitivitty = 94.1%, specificity = 54.5%). When the cut-off values of SUVmax and SUVpeak were set at 10.7 and 6.9 respectively, the maximum performances for predicting recurrence were obtained. Kaplan-Meier analyses showed that histologic subtype, SUVmax, and SUVpeak were risk factors that associated with recurrence-free survival (P = 0.02, ＜0.001, and 0.001, respectively).Conclusions: The SUV value and CT features on 18F-FDG PET/CT imaging may increase the confidence in diagnosis and subtype distinguish of RPLPS. When inflammatory liposarcoma was excluded, patients with SUVmax > 10.7 or SUVpeak > 6.9 suggest a poor prognosis.