BackgroundBreast cancer is the most frequent cancer in women and remains the second leading cause of death in Western countries. It represents a heterogeneous group of diseases with diverse tumoral behaviour, treatment responsiveness and prognosis. While major progress in diagnosis and treatment has resulted in a decline in breast cancer-related mortality, some patients will relapse and prognosis in this cohort of patients remains poor. Treatment is determined according to tumor subtype; primarily hormone receptor status and HER2 expression. Menopausal status and site of disease relapse are also important considerations in treatment protocols.Main bodyStaging and repeated evaluation of patients with metastatic breast cancer are central to the accurate assessment of disease extent at diagnosis and during treatment; guiding ongoing clinical management. Advances have been made in the diagnostic and therapeutic fields, particularly with new targeted therapies. In parallel, oncological imaging has evolved exponentially with the development of functional and anatomical imaging techniques. Consistent, reproducible and validated methods of assessing response to therapy is critical in effectively managing patients with metastatic breast cancer.ConclusionMajor progress has been made in oncological imaging over the last few decades. Accurate disease assessment at diagnosis and during treatment is important in the management of metastatic breast cancer. CT (and BS if appropriate) is generally widely available, relatively cheap and sufficient in many cases. However, several additional imaging modalities are emerging and can be used as adjuncts, particularly in pregnancy or other diagnostically challenging cases. Nevertheless, no single imaging technique is without limitation. The authors have evaluated the vast array of imaging techniques – individual, combined parametric and multimodal - that are available or that are emerging in the management of metastatic breast cancer. This includes WB DW-MRI, CCA, novel PET breast cancer-epitope specific radiotracers and radiogenomics.

F18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) plays a crucial role in tumour diagnosis, staging, and therapy response evaluation of various cancer types and has been a standard imaging modality used in clinical oncology practice for many years. However, it has certain limitations in evaluating some particular gastrointestinal cancer types due to low FDG-avidity or interphering physiological background activity. Fibroblast activation protein (FAP), a protein of the tumour microenvironment, is overexpressed in a wide range of cancers which makes it an attractive target for both tumour imaging and therapy. Recently, FAP-targeted radiopharmaceuticals are widely used in clinical research and achieved great results in tumour imaging. Considering the limitations of FDG PET/CT and the lack of physiological FAP-targeted tracer uptake in liver and intestinal loops, gastrointestinal cancers are among the most promising indications of FAP-targeted imaging. Herein, we present a comprehensive review of FAP-targeted imaging in gastrointestinal cancers in order to clarify the current and potential future role of this class of molecules in gastrointestinal oncology.