Advances in Imaging to Assess Response in Rectal Cancer

Inclusion Criteria: * Histologically confirmed rectal adenocarcinoma. * T stage 3b or above and/or high risk factors eg. EMVI, nodal disease. * Participant able to give written informed consent. * Male or non-pregnant female ≥18 years of age. * Scheduled to undergo radical radiotherapy. * Patients willing and able to comply with the protocol for the duration of study. Exclusion Criteria: * Contra-indications to MRI, such as claustrophobia, excessive body weight, MRI unsafe implants, ferrous metal in the body, insufficient information on prior surgeries. MRI conditional implants where conditions cannot be met (e.g pacemakers). * Any previous radiotherapy to the pelvis. * Inflammatory bowel disease. * Other severe or uncontrolled systemic disease or evidence of any other significant disorder or lab finding that makes it undesirable for the patient to participate in the study, as determined by the treating clinician. * History of physical or psychiatric disorder that would prevent informed consent and compliance with the protocol. * Patients with de-functioning stoma. * Major surgery within 28 days prior to trial entry.