Preoperative FDG PET/CT tumor markers outperform MRI based markers for the prediction of lymph node metastases and aggressive disease in endometrial cancer

281 Objectives: To compare the diagnostic accuracy of preoperative tumor markers derived from FDG PET/CT and MRI for the prediction of lymph node metastases (LNM) and aggressive disease in endometrial cancer (EC) patients. Methods: Preoperative whole-body FDG PET/CT and pelvic MRI were prospectively performed in 215 consecutive patients with histologically confirmed EC. The FDG PET/CT based tumor parameters maximum and mean standardized uptake value (SUVmax, SUVmean) and metabolic tumor volume (MTV) were analyzed together with the MRI based tumor volume (VMRI) and mean tumor apparent diffusion coefficient (ADCmean). Imaging parameters were explored in relation to surgicopathological stage and tumor grade. Receiver operating characteristic (ROC) curves were generated yielding optimal cut-offs for imaging parameters, and regression analyses were used to assess their diagnostic performance for prediction of LNM and outcome. Results: MTV and VMRI were the only imaging parameters significantly associated with deep myometrial invasion (p 27 ml and VMRI>10 ml yielded comparable sensitivity (81% for both), but MTV>27 ml had higher specificity (74% vs. 60%), accuracy (75% vs. 62%) and odds ratio (12.2 vs. 6.5) compared to VMRI>10 ml. Patients with higher SUVmean and MTV had significantly reduced recurrence/progression-free survival with univariate hazard ratios of 1.148 (p=0.03) and 1.003 (p=0.02), whereas high SUVmax and VMRI only tended to the same (p=0.12 and 0.18, respectively). Conclusions: Tumor markers derived from FDG PET/CT outperform MRI markers for the prediction of LNM and poor survival in EC. MTV>27 ml yielded high diagnostic performance for predicting aggressive disease and represents a promising supplement to conventional PET/CT reading in EC.