Measurement of solid tumor response to treatment relies mainly on imaging. WHO tumor response criteria and, more recently, RECIST (response evaluation criteria in solid tumors) have provided means to objectively measure tumor response in clinical trials with imaging. These guidelines have been rapidly adopted in clinical practice to monitor patient treatment and for therapy planning. However, relying only on anatomical information is not always sufficient when evaluating new drugs that will reduce a tumor's functionality while preserving its size. Finding more reliable and reproducible measures of tumor response is one of the most important and difficult challenges facing modern radiology as it requires an entirely new approach to imaging. The aim of this book is to address the assessment of response to treatment by adopting a multidisciplinary perspective, just as occurs in real life in a comprehensive cancer center. Oncologists and imaging experts consider two cancer models, locally advanced disease and metastatic disease, jointly exploring both conventional and advanced means of measuring response to standard treatment protocols and new targeted therapies.