RESUMO
BACKGROUND: Accurate nodal restaging is becoming clinically more important in patients with locally advanced rectal cancer (LARC) with the emergence of organ-preserving treatment after a good response to neoadjuvant chemoradiotherapy (nCRT). PURPOSE: To evaluate the accuracy of MRI in identifying negative N status (ypN0 patients) in LARC after nCRT. MATERIAL AND METHODS: 191 patients with LARC underwent MRI before and 6-8â¯weeks after nCRT and subsequent total mesorectal excision. Short-axis diameter of mesorectal lymph nodes was evaluated on the high resolution T2-weighted images to compare MRI restaging with histopathology.. RESULTS: 146 and 45 patients had a negative N status (ypN0) and positive N status (ypNâ¯+â¯), respectively. On restaging MRI, the 70â¯% reduction in size of the largest node was associated with an area under the curve (AUC) of 0.818 to predict ypN0 stage, with a sensitivity of 93.3â¯% and a negative predictive value (NPV) of 95.4â¯%. No nodes were observed in 38 pts (37 pts ypN0 and 1 patient ypNâ¯+â¯), with sensitivity and NPV of nodes disappearance for ypN0 stage of 93.3â¯% and 92.5â¯% respectively. A 2.2â¯mm cut-off in short-axis diameter was associated with an AUC of 0.83 for the prediction of ypN0 nodal stage, with sensitivity and NPV of 79,5% and 91.1â¯% respectively. CONCLUSION: A reduction in size of 70â¯% of the largest limph-node on MRI at rectal cancer restaging has high sensitivity and NPV for prediction of ypN0 stage after nCRT. The high NPV of node disappearance and of aâ¯≤â¯2.2â¯mm short-axis diameter is confirmed.