Background: In cancer, a response to therapy implies a reduction in the volume or activity of localized and/or metastatic tumors. In localized upper gastrointestinal cancer, there is no accepted definition of clinical response; however, tumor shrinkage is frequently observed when preoperative therapy is administered. As patients with upper gastrointestinal cancers often undergo multimodal therapy, it is therefore imperative that new definitions for assessing the response to preoperative therapy be established. Methods: We reviewed the development of response criteria from a historical perspective, with particular emphasis on the criteria used to assess upper gastrointestinal cancers. Results: Observing the response to preoperative therapy appears to make it possible to distinguish between favorable and unfavorable clinical biology in the cancer. Patients who experience a response to preoperative treatment appear to fare better in terms of overall survival than those whose cancers do not respond. We reviewed the published results regarding the response to preoperative therapy and the implications of this for patients. Conclusions: This review of the literature suggests that a variety of tools are available for defining the response to preoperative therapy and that these need to be exploited. Developing reliable methods of assessing the response will improve the individualization of therapy for patients with gastroesophageal cancer. There is a strong need for surrogate markers for efficacy in order to assess responses that are capable of predicting patient outcome.
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