Medical oncology depends on an accurate assessment of tumour response to therapy.  In the case of solid tumours, radiological imaging has assumed a dominant role in assessing response, because it can provide reliable and mostly objective measurements of tumour size.  RECIST (Response Evaluation Criteria in Solid Tumours) is one of a family of systems with definitions and rules for measuring tumours and assigning them to discrete categories of response.  RECIST has emerged as the most common methodology for determining response to therapy in the field of clinical trials; its principles may be applied to the general practice of oncology, as well.  The results of clinical trials are also of scientific merit, and, therefore, RECIST has become an accepted measure of efficacy both for regulatory approval and for advancing scientific knowledge regarding novel therapies.

Before RECIST can be applied productively, however, it is essential to understand its assumptions and limitations.  In this presentation, we will examine RECIST and other similar image-based methodologies, with an emphasis on both objective and subjective criteria in assessing tumor response.   Specific problem areas, such as non-measurable disease and “pseudoprogression,” will be addressed.  In this richly illustrated talk, Dr. Raskin will draw on his experience with thousands of patient encounters in clinical trials in order to demonstrate the practical use of image-based criteria in the context of randomized clinical trials.