Nodal staging in rectal cancer: why is restaging after chemoradiation more accurate than primary nodal staging?

Purpose: This study aims to explore the influence of chemoradiation treatment (CRT) on rectal cancer nodes and to generate hypotheses why nodal restaging post-CRT is more accurate than at primary staging.

Methods: Thirty-nine patients with locally advanced rectal cancer underwent MRI pre- and post-CRT. All visible mesorectal nodes were measured on a 3D T1-weighted gradient echo (3D T1W GRE) sequence with 1-mm(3) voxels and matched between pre- and post-CRT-MRI and with histology by lesion-by-lesion matching.