Thesis

92 Chapter 6 Table 1. Methods of response evaluation Method MR sequence(s) Score Dichotomized score Complete response Residual tumor mrTRG T2W-MRI (post-CRT) · 1 = no/minimal fibrosis · 2 = dense fibrotic scar without macroscopic tumor signal · 3 = fibrosis predominates but there are obvious areas of tumor signal · 4 = tumor signal predominates with little/minimal fibrosis · 5 = tumor signal only: no fibrosis, includes cases with progression of tumor 1-2* 3-5 Modified TRG T2W-MRI + DWI (post-CRT) · 0 = No tumor signal on T2W-MRI, no diffusion restriction (complete regression) · 1 = Predominant fibrosis on T2W-MRI, focal diffusion restriction (intermediate regression) · 2 = Predominant tumor on T2W-MRI, focal or masslike diffusion restriction (poor regression) 0 1-2 DWI pattern T2W-MRI (pre and post-CRT) + DWI (post-CRT) · A - = normalized rectal wall, no diffusion restriction · A+ = bulky solid residual tumor mass with corresponding diffusion restriction · B = circular/irregular tumors (pre-CRT) with irregular/spiculated fibrosis (post-CRT) B- = no diffusion restriction B+ = scattered foci of diffusion restriction · C = semicircular tumors (pre-CRT) with semicircular/focal fibrosis (post-CRT) C- = no diffusion restriction C+ = focal diffusion restriction at inner margin of fibrosis · D = polypoid tumor (pre-CRT) with focal fibrosis at site of polyp stalk (post-CRT) D- = no diffusion restriction D+ = focal diffusion restriction at site of stalk A-^ CDA+ B+/- C+ D+ Split scar T2W-MRI (post-CRT) · 0 = Split scar present · 1 = Split scar absent 0 1 *Cut off chosen based on results of a meta-analysis by Jang et al. assessing the mrTRG to diagnose a pathologic complete response, which showed highest sensitivity for mrTRG1-2 (Eur Radiol 2020;30(4):2312-2323). ^ Based on cut offs recommended in the original publication by Lambregts et al. describing the DWI pattern approach (Dis Colon Rectum 61(3):328-337)

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