Radiologic Assessment of Response to Therapy: Comparison of RECIST Versions 1.1 and 1.0

Improvements in radiologic imaging technology and therapeutic options available for management of tumors have necessitated the revision of guidelines for the imaging-based assessment of tumor response to therapy. The purpose of this article is to familiarize radiologists with the modifications to the Response Evaluation Criteria in Solid Tumors (RECIST) that have been incorporated in the latest version of the guidelines, RECIST 1.1. The most important differences between this version and the previous one, RECIST 1.0, include reductions in the maximum number of lesions per patient and per organ that may be targeted for measurement, augmentation of the criteria defining progressive disease, additional guidelines for reporting findings of lesions that are too small to measure and for measuring lesions that appear to have fragmented or coalesced at follow-up imaging, new criteria for characterizing lymphadenopathy, new criteria for selecting bone lesions and cystic lesions as targets for measurement, and the inclusion of findings at positron emission tomography among the indicators of disease response.