Risk assessment in liposarcoma patients based on FDG PET imaging

Purpose: Tumor grade and subtype are considered standard parameters for risk assessment in patients with liposarcoma. The aim of this study was to assess the clinical value of [F-18] fluorodeoxyglucose (FDG) PET-derived maximum standardized uptake value (SUVmax) for prediction of outcome in liposarcoma patients. Methods: F-18-FDG PET was performed in 54 patients with liposarcoma prior to therapy. SUVmax was calculated for each tumor and results were correlated with tumor grade, subtype, and relapse-free survival. Results: SUVmax ranged from 0.4 to 15.9 ( mean 3.6) and was significantly lower in grade I than in grade II and grade III tumors. SUVmax was 2.3 +/- 1.7, 3.5 +/- 1.5, 4.8 +/- 2.5, and 5.6 +/- 5.8 in well-differentiated, myxoid/round cell, dedifferentiated, and pleomorphic subtypes, respectively. Borderline differences (p= 0.059) were found between tumor SUVmax in patients with and without relapse. Using a SUV of 3.6 as cut-off, the accuracy in predicting a relapse was 75%. Tumor grade yielded a lower accuracy for predicting relapse (50%), as did tumor subtype (35%). In Kaplan-Meier survival analysis, patients with a SUVmax > 3.6 had a significantly shorter disease-free survival of 21 months compared with 44 months in patients with a SUVmax <= 3.6. Tumor grading and tumor subtype did not yield significant differences. Conclusion: Pretherapy tumor SUV obtained by FDG PET imaging was a more useful parameter for risk assessment in liposarcoma than tumor grade or subtype. A SUVmax of more than 3.6 resulted in a significantly reduced disease-free survival and identified patients at high risk for developing early local recurrences or metastatic disease.