Criteria of metabolic response to immunotherapy.

Therapy response assessment is one of the most challenging indications of imaging studies. In clinical trial patients it is usually measured with standardized response criteria. However, in clinical practice, many studies are carried out in which the clinical question is whether or not the treatment is being effective. Answering this question is one of the greatest challenges for diagnostic imaging physicians, especially when a new treatment modality is being introduced, whose effects on tumoral lesions are initially poorly understood. We have an essential role in the introduction of new therapies, assessing their effects and benefits. Knowledge of these effects has led to the development of many response criteria that, despite being applicable only in clinical trials, offer us information on how to interpret findings in clinical practice.