This is a great question as clearly liver MRI has a greater sensitivity for detecting metastatic disease than other modalities. Ultimately, the decision to perform another staging investigation depends on the balance between cost, available resources and inconvenience to the patient versus any potential benefit arising from up-staging. This consideration needs to be risk-assessed for each individual patient. For healthcare systems that can afford it, the trend is for liver MRI at initial staging in those patients that are high risk for liver metastases and are going to be suitable candidates for radical treatment for stage 4 disease. Therefore patient’s wishes, fitness and tumour characteristics seen on the pelvic MRI such as extra-mural venous invasion and advanced T-stage will inform this decision. In our unit, we will not routinely perform liver MRI unless the CT has shown an abnormality. Occasionally in a young fit patient with an extremely high risk primary tumour, we have gone ahead and arranged both pelvic and liver MRI at the outset. In the age of total neoadjuvant therapy for high risk cancers, it is useful to know what the baseline liver imaging is like, as the first treatment will be chemotherapy and most liver metastases will re-appear at some point in the future even if they are not seen after neoadjuvant therapy. Bear in mind that a liver MRI is a prolonged and unpleasant investigation for the patient.

A CT scan is still the most appropriate screening investigation in terms of cost, convenience and patient acceptance. In addition it provides information regarding any extra-hepatic spread which will dictate subsequent therapy.