18F-Fluorodeoxiglucose Positron Emission Tomography for the Evaluation of Neoadjuvant Therapy Response in Esophageal Cancer Systematic Review of the Literature

Neoadjuvant treatment is a relatively new therapeutic approach for locally advanced esophageal cancer. Response assessment is crucial for the treatment of these patients. Cross sectional imaging has traditionally being used as the elective method of response assessment. Recently, 18F fluorodeoxyglucose- positron emission tomography (FDG-PET) has emerged as a new valuable tool defining therapy response assessment in other tumors. Aim: We systematically reviewed the increasing number of publications appearing in the literature analyzing the utility of FDG-PET in the evaluation of neoadjuvant therapy response assessment. Methods: We performed a bibliographic search according to the COSI protocol and selected only prospective studies to achieve the highest levels of evidence. Quality assessment was defined with the QUADAS questionnaire. Results: Eight of 237 potentially relevant publications were selected for the analysis. Ranged sensitivity, specificity, positive predictive value, and negative predictive value for primary tumor response assessment were 27.3% to 93.3%, 41.7% to 95.2%, 70.8% to 93.3% and 71.4% to 93.5%, resipectively, and for N restaging, 16.0% to 67.5%, 85.7% to 100%, 33% to 100% and 91.7% to 93.3%, respectively. The heterogeneity of the publications ruled out the possibility of meta-analysis. FDG-PET is more precise compared with computed tomography in the evaluation of induction therapy response assessment. Conclusion: FDG-PET seems to be the best available imaging modality for neoadjuvant therapy response assessment in esophageal cancer. :But more prospective studies with larger populations are needed to confirm the power of this imaging tool in this aim and to determine the best analytical interpretation method and threshold to differentiate responders from nonresponding patients.