Immunotherapy may not always prove effective and Sanjiv Sam Gambhir, MD, PhD, from Stanford University School of Medicine, Stanford, CA, believes it is extremely important to understand why this is. Prof. Gambhir discusses the importance of molecular imaging in establishing, at the molecular level, why immunotherapy is not always successful, and is hopeful that molecular imaging will support the development of better immunotherapeutic approaches. This video was recorded at the 2018 National Cancer Research Institute (NCRI) Cancer Conference, held in Glasgow, UK.