Conventional Radiological Techniques and PET-CT in Treatment Response Evaluation in Post-Radiotherapy Setting

Abstract

Early recognition of treatment success or failure can impact on patient survival. Traditionally, this assessment relies upon the anatomical measurement of disease, such as CT evaluation using the Response Evaluation Criteria in Solid Tumors (RECIST). However, such measurements are of limited value following radiotherapy. The challenge of determining the presence or absence of viable tumor within residual masses following radiotherapy provides a convincing rationale for incorporating functional imaging into response assessment protocols. PET/CT employs radioactive tracers to assess molecular characteristics of tissues. PET/CT in radiotherapy response assessment is useful as a molecular response to radiotherapy, may precede anatomical response, and allows a more accurate estimate at an earlier stage. Besides the use of specific tracers, it will enable more reliable tumor discrimination from treatment-related inflammation or fibrosis. The chapter includes the advantages and limitations of conventional imaging and PET/CT in the postradiotherapy setting and discusses the potential benefits and pitfalls of image interpretation.