Summary

 With our increased understanding of cancer cell biology, molecular imaging offers a strategic bridge to oncology. This complements anatomic imaging, particularly magnetic resonance (MR) imaging, which is sensitive but not specific. Among the potential harms of false positive findings is lowered adherence to recommended surveillance post-therapy and by persons at increased cancer risk. Positron emission tomography (PET) plus computed tomography (CT) is the molecular imaging modality most widely used in oncology. In up to 40% of cases, PET-CT leads to changes in therapeutic management. Newer PET tracers can detect tumor hypoxia, bone metastases in androgen-sensitive prostate cancer, and human epidermal growth factor receptor type 2 (HER2)-expressive tumors. Magnetic resonance spectroscopy provides insight into several metabolites at the same time. Combined with MRI, this yields magnetic resonance spectroscopic imaging (MRSI), which does not entail ionizing radiation and is thus suitable for repeated monitoring. Using advanced signal processing, quantitative information can be gleaned about molecular markers of brain, breast, prostate and other cancers. Radiation oncology has benefited from molecular imaging via PET-CT and MRSI. Advanced mathematical approaches can improve dose planning in stereotactic radiosurgery, stereotactic body radiotherapy and high dose-rate brachytherapy. Molecular imaging will likely impact profoundly on clinical decision making in oncology. Molecular imaging via MR could facilitate early detection, especially in persons at high risk for specific cancers.