• Lotte Jacobs, Martijn Intven, Niels van Lelyveld, Marielle Philippens, Maarten Burbach, Kees Seldenrijk, Maartje Los, and Onne Reerink.
• *Department of Gastroenterology, St. Antonius Hospital Nieuwegein, Nieuwegein, The Netherlands †Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands ‡Department of Pathology, St Antonius Hospital Nieuwegein, Nieuwegein, The Netherlands §Department of Oncology, St Antonius Hospital Nieuwegein, Nieuwegein, The Netherlands.
• Ann. Surg. 2016 Mar 1; 263 (3): 522-8.

ObjectiveThis study investigates the predictive value of diffusion-weighted magnetic resonance imaging (DW-MRI) for good pathological response at different time points during and after preoperative chemoradiotherapy (CRT) in locally advanced rectal cancer.BackgroundPreoperative CRT followed by total mesorectal excision (TME) is the standard of care for locally advanced rectal cancer. The use of standard radical surgery in good treatment responders after CRT is being questioned.MethodsPatients with locally advanced rectal adenocarcinoma were treated with preoperative CRT followed by surgery. DW-MRI scans were performed before CRT, during the third week of CRT, 4 weeks post-CRT and presurgery. Tumor apparent diffusion coefficient (ADC) values were acquired from the DW-MRI scans. After surgery the pathological tumor regression grade was assessed according to the classification by Mandard et al [Cancer. 1994;73:2680-2686]. Patients with pathological complete or near-complete response (tumor regression grade 1-2) were classified as good responders (GRs).ResultsTwenty-two patients participated of which 9 were GRs (41%). Pre-CRT ADC values were lower in good versus moderate/poor responders (P = 0.04). ADC values during CRT and four weeks post-CRT were higher in GR. ADC values presurgery did not differ between response groups. For all time points the relative ADC increase (ΔADC) compared to the ADC pre-CRT was higher in GR (P < 0.001). The ΔADC during CRT and four weeks post-CRT were the best predictive parameters for pathological good response.ConclusionsThis study shows that DW-MRI is feasible to select good treatment responders during preoperative CRT for locally advanced rectal cancer.

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