88 Chapter 6 Methods Patient selection This study was conducted as a side-study of an institutional review board-approved retrospective multicentre study on multiparametric imaging for tumor response evaluation in locally advanced rectal cancer. Due to the retrospective nature of the study, informed consent was waived. As part of this study, the imaging and clinical outcome data of 1037 patients (2010–2018) were retrospectively collected from 10 centers in the Netherlands, including 1 university hospital, 8 large teaching hospitals, and 1 comprehensive cancer center. For the current study, we selected from this cohort a semi-random sample of n = 90 patients taking into consideration that data of all 10 study centers had to be represented in the cohort and ensuring a clinically representative sample in terms of baseline cTN-stage and response outcomes with a sufficient number of complete responders (being the primary study outcome) to allow meaningful statistical analyses. Study inclusion and exclusion criteria are detailed in Fig. 1. Figure 1 Patient in- and exclusion flowchart
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