76 Chapter 5 Figure 2 Examples showing how IOA and ymrT-/ypT-stage concordance were affected by the degree of tumour regression. The left case is a patient with a complete tumour regression (pTRG 1). The restaging T2W-MRI show predominant fibrosis. There is no suspicious signal on DWI (* indicates high signal caused by T2 shine through of intraluminal fluid). There was considerable variation between readers and the majority of readers overstaged this case as residual tumour. The middle patient is a pTRG3 case. The restaging T2W-MRI shows irregular and slightly heterogeneous fibrosis; on DWI a rim-like high signal (suggestive of residual tumour) is visible at the inner margin of the fibrosis. There was substantial variation in the ymrT-stage assigned by the 22 readers. The right patient is a pTRG4 case. The restaging T2W-MRI shows predominant tumour with a clear corresponding high signal mass on DWI. Readers consistently and correctly staged this case as T3. Concordance between ymrT-stage and ypT-stage Table 2 shows a multilevel logistic regression model of the concordance (in%) between the ymrT-stage and the final ypT-stage, including subgroup analyses for patients with predominant tumour (pTRG4-5) versus patients with predominant fibrosis (pTRG1-3). Results of the corresponding multilevel logistic regression model are provided in detail in Supplement 1. The relation between ymrT-/ypT-stage concordance and pTRG is further illustrated in Figure 1 and representative imaging examples are provided in Figure 2.
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