There is a widening therapeutic opportunity for treating ‘oligometastatic’ cancer with radical intent. However, both oligometastatic cancer and, importantly, the patients who benefit from intervention remain poorly defined. The tumour biology is heterogeneous and patient outcomes are variable, suggesting improved biomarkers are needed to select treatment strategies appropriately.

Multimodal imaging already has a central role in defining the disease burden in patients with limited metastatic cancer. However, modern imaging techniques can also provide additional phenotypic information, which may improve tumour characterisation. In contrast to many other potential biomarkers, imaging can is non-invasive, and can assess multiple disease sites at multiple time-points across treatment; it may therefore have particular utility in the metastatic setting. Here, we discuss the existing and potential future roles for imaging as a biomarker in oligometastatic colorectal cancer, focusing on the capacity to assess a dynamic, heterogeneous disease.