Comparison of FDG PET-CT and MRI in lymph node staging of endometrial cancer

Objectives To compare the diagnostic accuracy of F-18 FDG PET with that MRI for detecting metastatic lymph nodes in preoperative staging of endometrial cancer.

Methods Between January 2005 and Jul 2010, 103 patients with endometrial cancer underwent both FDG-PET and abdominal MRI before radical hysterectomy or pelvic lymphadenectomy (mean age, 49.5 ± 24.5 y). Malignancy criteria of lymph node were a lymph node diameter of 1 cm or more at MRI and a focally increased FDG uptake on PET. The findings of FDG-PET and MRI were compared with histologic findings

Results A total of 72 metastatic LNs of 509 LNs (14%) were identified in 17 of 103 patients (17%). Histologic examination revealed I to IIIA stage cancer in 86 patients and IIIC1 to IV stage cancer in 17 patients. On a patient basis, node staging resulted in sensitivities of 0.77 with FDG-PET and 0.46 with MRI and specificities of 0.96 with FDG-PET and 0.96 with MRI. The negative predictive value (NPV) of FDG-PET was 0.97 and that of MRI, 0.92. The maximal standardized uptake value (maxSUV) of the primary lesions in PET/CT ranged from 1.5 to 26.2, with a mean of 7.9. For comparison, 24 patients with physiologic accumulation of FDG in the uterus cavity without a known gynecologic malignancy were enrolled, and maxSUV of uterus ranged from 2.3 to 7.1, with a mean of 3.78. The cut-off value is 4.8 with optimal sensitivity 0.60 and specificity 0.92.

Conclusions FDG-PET showed better sensitivity than MRI for detecting metastatic lymph nodes in patients with endometrial cancer. MaxSUV of primary lesions was higher than that of physiologic uptake, but there were considerable overlapping range