65 Evolutions in rectal cancer MRI staging and risk stratification in the Netherlands 4 risk factor, it has not (yet) been widely implemented as a main treatment determinant in current clinical guidelines. Looking at our current results, EMVI by itself would have had only a minor additional impact on treatment decision making, as the presence of EMVI almost exclusively went hand in hand with the presence of other high-risk features (cT3cd-4 stage, cN+ stage, cMRF+ stage). Only in 7 cases (1.2%) EMVI was the only high-risk feature present on MRI. Finally, our study showed a vast increase in the use of structured (template) reporting, as well as improved completeness of reporting for several items including MRF invasion, anal sphincter invasion, lateral nodal involvement and tumor morphology. These findings are likely related to one another and in line with previous reports demonstrating that template reports are superior to free-text reports in terms of completeness of reporting (24,25). Additional benefits of structured reporting described in the literature include improved clarity and consistent use of terminology across practices which in turn guarantees better communication in imaging (26-28). Overall, it has been suggested that implementation of structured reporting templates can improve the quality of MRI reporting for rectal cancer compared to free-text formats, and leads to higher satisfaction levels from referring clinicians (29-30). Somewhat surprisingly, the percentage of structured reports decreased in the third part of the study period, after an initial steep increase in the second part of the study. This can be attributed to the fact that two of the centers in the cohort with the highest rate of structured reporting were relatively underrepresented in the third part of the study period. Our study has some limitations, in addition to its retrospective study design. As before mentioned, all re-evaluations using updated staging criteria were done by single experienced rectal MRI reader, whereas original interpretations and reports were done by multiple readers as part of routine clinical practice. We have no detailed information on the experience level of these readers and it is conceivable that at least part of the discrepant findings after re-evaluation of the images can be attributed to variations in reader experience rather than variations in guidelines and criteria used. Along this line, we have no way of knowing which criteria were used by the various radiologists while performing their original staging reports. However, we do know that updated guideline criteria (in particular for nodal staging) were not yet available or published during the early years of the study period, and therefore likely not used. In conclusion, this study shows that updated concepts of risk stratification in rectal cancer such as cT3-substaging, revised criteria for nodal staging and reporting of EMVI have increasingly been adopted during the last decade in teaching hospitals in The Netherlands. This was accompanied by increased use of template reporting and overall improved completeness of reporting. Use of updated guideline criteria resulted in
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