Performance of gadofosveset-enhanced MRI for staging rectal cancer nodes: can the initial promising results be reproduced?

OBJECTIVES: A previous study showed promising results for gadofosveset-trisodium as a lymph node magnetic resonance imaging (MRI) contrast agent in rectal cancer. The aim of this study was to prospectively confirm the diagnostic performance of gadofosveset MRI for nodal (re)staging in rectal cancer in a second patient cohort. METHODS: Seventy-one rectal cancer patients were prospectively included, of whom 13 (group I) underwent a primary staging gadofosveset MRI (1.5-T) followed by surgery (+/- preoperative 5 x 5 Gy) and 58 (group II) underwent both primary staging and restaging gadofosveset MRI after a long course of chemoradiotherapy followed by surgery. Nodal status was scored as (y)cN0 or (y)cN+ by two independent readers (R1, R2) with different experience levels. Results were correlated with histology on a node-by-node basis. RESULTS: Sensitivity, specificity and area under the receiver operating characteristics curve (AUC) were 94 %, 79 % and 0.89 for the more experienced R1 and 50 %, 83 % and 0.74 for the non-experienced R2. R2's performance improved considerably after a learning curve, to an AUC of 0.83. Misinterpretations mainly occurred in nodes located in the superior mesorectum, nodes located in between vessels and nodes containing micrometastases. CONCLUSIONS: This prospective study confirms the good diagnostic performance of gadofosveset MRI for nodal (re)staging in rectal cancer. KEY POINTS: * Gadofosveset-enhanced MRI shows high performance for nodal (re)staging in rectal cancer. * Gadofosveset MRI may facilitate better selection of patients for personalised treatment. * Results can be reproduced by non-expert readers. * Experience of 50-60 cases is required to achieve required expertise level. * Main pitfalls are nodes located between vessels and nodes containing micrometastases.