Gadofosveset-enhanced MRI for nodal staging in rectal cancer:predictive criteria: OP26

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Aim:Recently we showed that MRI using a new lymph-node contrast (gadofosveset) has high accuracy for nodal staging in rectal cancer. Aim of this study was to determine the most accurate imaging criteria for nodal evaluation on gadofosveset-MRI.Method:Thirty-three patients underwent T1-weighted MRI before and after administration of gadofosveset-contrast. For each node the signal intensity (SI) was measured onpre-and post-contrast MRI. Furthermore, thepresence of a nodal relief effect was scored. Finally, nodes were scored (using a 5-point confidence score) by an MR-rectum expert, based on visual evaluation of SI and nodal relief. Nodes were drawn on an anatomical template for lesion-by-lesion histologic validation.Results:Two hundred and eighty-nine nodes (55 malignant) were analysed. Onpre-contrast MRI, SI did not differ between benign and malignant nodes. On gadofosveset-MRI, SI was significantly higher in the benign nodes (P < 0.0001), which resulted in an area under the ROC-curve (AUC) of 0.74. The combination of SI and nodal relief rendered an AUC of 0.88. When analysed visually, AUC for discrimination of metastatic nodes was 0.92.Conclusion:Only benign nodes show uptake of gadofosveset-contrast. The best criteria are nodal signal intensity and relief. When analysed visually, these criteriaprovide high accuracy for discrimination of metastatic nodes.

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