Anti-VEGF molecular targeted therapies in common solid malignancies: comprehensive update for radiologists

Angiogenesis is an essential component of the growth and dissemination of solid malignancies and is mediated by several proangiogenic factors. The most widely studied proangiogenic factor is vascular endothelial growth factor (VEGF). A major class of molecular targeted therapies (MTTs) inhibit the VEGF axis and are referred to as antiangiogenic MTTs. There are two main types of anti-VEGF MTTs: drugs targeting circulating VEGF and drugs interfering with the activity of the VEGF receptors. The cancers against which antiangiogenic MTTs have had the greatest effect are gliomas, non-small cell lung cancer, colorectal cancer, hepatocellular carcinoma, renal cell carcinoma, and gastrointestinal stromal tumor. These cancers respond to antiangiogenic MTTs in a different way than they respond to conventional chemotherapy. Instead of the traditional Response Evaluation Criteria in Solid Tumors (RECIST), each of these cancers therefore requires its own individualized treatment response criteria (TRC). Examples of individualized TRC include the Response Assessment in Neuro-oncology (RANO) criteria for gliomas, modified RECIST for hepatocellular carcinoma, and Morphology, Attenuation, Size, and Structure (MASS) criteria for renal cell carcinoma. Furthermore, antiangiogenic MTTs have a unique spectrum of class-specific and drug-specific toxic effects, some of which can be detected at imaging. Increasing use of antiangiogenic MTTs in clinical practice necessitates that radiologists be aware of these drugs, their response patterns, and TRC as well as their toxic effect profiles.