64 Chapter 4 lines (particularly in the United States) it remains routine practice to give neoadjuvant treatment to any cT3 tumor, regardless of invasion depth. The high proportion (35.7%) of nodal downstaging can probably be attributed to the fact that images were all assessed by a dedicated reader with consistent use of the nodal staging criteria as detailed in the structured report template proposed by ESGAR, while the original reports were generated by a variety of radiologists from the participating centers and likely with varying criteria. Although we obviously cannot be sure which criteria were used by these radiologists, it is likely to assume that at least part of the scans were assessed using traditional (size-based) criteria considering that a considerable proportion of the cohort originated from <2014, i.e. before updated criteria on nodal staging including nodal morphology were adopted by the 2014 updates of the Dutch guidelines and before the most recent ESGAR consensus guidelines were published. As demonstrated in previous literature, use of size-based criteria may result in substantial nodal overstaging (16, 17). A population-based study of 14.018 patients in the Netherlands treated for rectal cancer between 2009 and 2014 showed a substantial decrease in the use of preoperative radiotherapy (versus surgery only) after implementation of the Dutch national guideline updates in 2014, which was accompanied by a marked increase in the specificity of MRI for nodal staging (from 62.9% in 2013 to 73.2% in 2014), indicating a decrease in nodal overstaging (22). A more recent Dutch study by Detering et al. covering the period 2011-2017 (total 21.385 patients) confirmed a significant decrease in the use of preoperative radiotherapy for early-stage tumors in the period following the 2014 guideline updates. Again, the authors suggested that this decrease may at least in part be contributed to the updated guidelines on nodal staging that increased the threshold to diagnose nodes as malignant on MRI (23). According to the ESGAR (and Dutch) guidelines, only nodes with a short-axis diameter of ≥9 mm are immediately staged as N+ based on size only. For nodes with a short-axis of 5-8 mm or <5 mm, two or even three additional morphologically suspicious criteria (round shape, irregular border, heterogeneous signal) are required in order to call a node malignant (3,14). Our results confirm trends shown in previous population studies that this approach leads to substantial downstaging of nodes, compared to use of traditional (size-based) criteria. With respect to EMVI, we observed that this is a risk factor that is increasingly being reported in routine practice, reflecting an increased awareness of EMVI as a relevant prognostic feature to include in routine reporting. While in the first part of the study period (2011-2014) EMVI was only reported in <5% of the cases, this number increased significantly to 37.4% in the final years of the study period up to 2018. The cases where EMVI was not reported included a substantial number of cT1-2 cases where reporting of EMVI will in most cases be considered as less or irrelevant. Although EMVI is increasingly acknowledged and adopted in structured reporting templates as a relevant prognostic
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