PT - JOURNAL ARTICLE AU - Mark A Sellmyer AU - Iris K Lee AU - David A Mankoff TI - Building the Bridge: Molecular Imaging Biomarkers for 21<sup>st</sup> Century Cancer Therapies AID - 10.2967/jnumed.121.262484 DP - 2021 Aug 01 TA - Journal of Nuclear Medicine PG - jnumed.121.262484 4099 - http://jnm.snmjournals.org/content/early/2021/08/26/jnumed.121.262484.short 4100 - http://jnm.snmjournals.org/content/early/2021/08/26/jnumed.121.262484.full AB - Precision medicine, where the molecular underpinnings of the disease are assessed for tailored therapies, has greatly impacted cancer care. In parallel, a new pillar of therapeutics has emerged with profound success, including immunotherapies such as checkpoint inhibitors and cell-based therapies. Nonetheless, it remains essential to develop paradigms to predict and monitor for therapeutic response. Molecular imaging has the potential to add substantially to all phases of cancer patient care: predicative, companion diagnostics can illuminate therapeutic target density within a tumor, and pharmacodynamic imaging biomarkers can complement traditional modalities to judge a favorable treatment response. This “Focus on Molecular Imaging” article discusses the current role of molecular imaging in oncology and highlights an additional step in clinical paradigm termed a “therapeutic biomarker,” which serves to assess whether next generation drugs reach their target to elicit a favorable clinical response.