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 [(18)F]fluorodeoxyglucose (FDG) PET-derived maximum standardized uptake value (SUV(max)) for prediction of outcome in liposarcoma patients.

METHODS: (18)F-FDG PET was performed in 54 patients with liposarcoma prior to therapy. SUV(max) was calculated for each tumor and results were correlated with tumor grade, subtype, and relapse-free survival.

RESULTS: SUV(max) 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. SUV(max) 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 SUV(max) 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 SUV(max) >3.6 had a significantly shorter disease-free survival of 21 months compared with 44 months in patients with a SUV(max) </=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 SUV(max) 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.