Development of imaging probes for bone cancer in animal models. A systematic review

Bone is a dynamic tissue that is constantly remodeled throughout the lifetime to ensure the integrity of the skeleton. Primary cancer cells disseminate into circulation, often extravasating to bone, where they interact with the bone marrow to grow and proliferate, disrupting the bone homeostasis. Although primary bone tumors account for less than 0.2% of all cancers, bone is a common site for the development of metastases, as its microenvironment provides the necessary conditions for the growth and proliferation of cancer cells. Metastases to the skeletal system are observed in up to 70% of all cancer patients and the growth of disseminated tumor metastases is a major cause of mortality. As widely known, a non-invasive diagnosis of bone tumors at early stages is of great importance to provide insights that will help on the decision of therapy regimen, improving treatment outcomes. Early diagnosis of bone metastases is also an important step for establishing palliative care as they may cause serious endocrine, hematologic, neurologic and orthopedic complications as well as intolerable pain. Therefore, development of new imaging techniques, imaging moieties, and animal models to mimic these bone conditions, play an important role in improving the clinical outcome of this disease. In this review, we will briefly describe the advantages and disadvantages of the currently available imaging techniques that aim at identifying bone tumors. In addition, we will provide an update on the animal models applicable at mimicking bone tumor characteristics, as well as describe recent advances on the development of new imaging probes, in the preclinical settings including targeted nanoparticles and radiopharmaceuticals.