Tumor response evaluation in oncology: Current update

Quantification of tumor burden and assessment of changes in tumor size after chemotherapy are commonly performed to evaluate treatment response in oncology trials. Validation and adoption of different criteria have been attempted in the past to achieve uniformity in scanning techniques and measurement metrics so that comparison of different oncological trials is feasible. Response assessment of solid tumors is usually consisted of either bidimensional (World Health Organization criteria) or unidimensional (Response Evaluation Criteria in Solid Tumors [RECIST] guidelines) measurement of tumors before and after chemotherapy. RECIST 1.1 criteria have been recently published. In this article, we try to provide a comprehensive review of the tumor response evaluation guidelines that were recently updated in attempts to overcome limitations of the previous criteria as well as incorporate recent advances in imaging techniques.