DIAGNOSTIC ACCURACY OF FEC-PET/CT, FDG-PET/CT AND DIFFUSION-WEIGHTED MRI IN DETECTION OF NODAL METASTASES IN SURGICALLY TREATED ENDOMETRIAL AND CERVICAL CARCINOMA.

PURPOSE Pre-operative nodal staging is important for planning treatment in cervical cancer (CC) and endometrial cancer (EC) but remains challenging. We compare nodal staging accuracy of 18F-ethyl-choline-(FEC)-PET/CT, 18F-Fluoro-deoxy-glucose-(FDG)-PET/CT and diffusion-weighted-MRI (DW-MRI) with conventional morphological MRI. EXPERIMENTAL DESIGN A prospective, multicentre observational study of diagnostic accuracy for nodal metastases was undertaken in 5 gyne-oncology centres. FEC-PET/CT, FDG-PET/CT and DW-MRI were compared to nodal size and morphology on MRI. Reference standard was strictly correlated nodal histology. Eligibility included operable CC stage=>1B1 or EC (grade 3 any stage with myometrial invasion or grade 1-2 stage=>II). RESULTS Among 162 consenting participants, 136 underwent study DW-MRI and FDG-PET/CT, and 60 underwent FEC-PET/CT. 267 nodal regions in 118 women were strictly correlated at histology (nodal positivity rate 25%). Sensitivity per-patient (n=118) for nodal size, morphology, DW-MRI, FDG- and FEC-PET/CT were 40%*, 53%, 53%, 63%* and 67% for all cases (*p=0.016); 10%, 10%, 20%, 30% and 25% in CC (n=40); 65%, 75%, 70%, 80% and 88% in EC (n=78). FDG-PET/CT outperformed nodal size (p=0.006) and size ratio (p=0.04) for per-region sensitivity. False positive rates were all <10%. CONCLUSIONS All imaging techniques had low sensitivity for detection of nodal metastases and cannot replace surgical nodal staging. The performance of FEC-PET/CT was not statistically different to other techniques that are more widely available. FDG-PET/CT had higher sensitivity than size in detecting nodal metastases. False positive rates were low across all methods. The low false positive rate demonstrated by FDG-PET/CT may be helpful in arbitration of challenging surgical planning decisions.