Description:

The combination of FDG-PET/CT and MRI at staging of rectal cancer in diagnosis is currently very little studied. The investigator have a unique opportunity to study this. Hypothetically, with PET/MR as one hybrid imaging method, alternatively as an additional method, it could increase the accuracy of rectal cancer of moderate and high risk type, especially at primary N-staging, but also in assessing other important prognostic factors such as T-staging, peritoneal involvement, metastasis to lateral lymph nodes, EMVI and MRF involvement. The same reasoning applies to the assessment of tumor regression after CRT. In the study, PET/MR is compared with PET/CT, diagnostic CT and MRI to evaluate the additional value of the hybrid imaging PET/MRI. The investigator also plan to evaluate how immunological, proliferative and prognostic biomarkers in blood and tumor tissue correlate with the radiological findings, and if the combination biomarker and radiology can provide additional prognostic information.