419. PROGNOSTIC RELEVANCE OF METABOLIC RESPONSE TO NEOADJUVANT CHEMOTHERAPY FOR ADENOCARCINOMA OF THE ESOPHAGUS AND ESOPHAGOGASTRIC JUNCTION

Background The prognostic value of the metabolic response to neoadjuvant therapy in patients with adenocarcinoma of the esophagus and esophagogastric junction (EAC) remains controversial. The aim of our single-center prospective trial was to evaluate the association of metabolic tumor and nodal response, as measured by 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT), with disease-free survival (DFS) in patient with EAC treated with neoadjuvant chemotherapy (NAC) followed by surgery. Methods Following the PET response criteria in solid tumors (PERCIST 1.0), PET/CT was performed before and after the third cycle of triplet NAC (epirubicine, cisplatina and 5-fluorouracil or capecitabine). The relative changes of the maximum, peak and mean standardized uptake value (ΔSULmax, ΔSULpeak, ΔSULmean), metabolic tumor volume (ΔMTV) and total leasion glycolysis (ΔTLG) in the primary tumor and ΔSULmax in the regional lymph nodes were analyzed in terms of prediction of DFS using Cox regression analysis. Results Some 94 patients with surgical resection were included between 2009 and 2015. Of the tumor metabolic response parameters, only ΔTLG and ΔMTV were associated with survival. Stepwise cutoff analysis found ΔTLG≥45% best predicted DFS (HR 0.25, p = 0.0018). Persistens of FDG-avidity of lymph nodes after NAC was associated with worse DFS (HR 2.63, p < 0.001). Multivariable analysis of preoperative variables (baseline characteristics and metabolic response) showed that only tumor ΔTLG≥45% and post-NAC nodal FDG-avidity were predictors of DFS. In the final multivariable model including postoperative variables, pN-stage and post-NAC nodal FDG-avidity remained the only independent variables associated with DFS. Conclusion ΔTLG is the most optimal metabolic parameter reflecting the response to NAC in the primary tumor, however it did not independently predict DFS after surgery. The complete metabolic response in the lymph nodes after NAC independently predicted the prognosis.