PS02.087: EARLY RESPONSE EVALUATION OF NEOADJUVANT THERAPY WITH PET/MRI TO PREDICT RESECTABILITY IN PATIENTS WITH ADENOCARCINOMA OF THE ESOPHAGOGASTRIC JUNCTION

Abstract

Abstract Background The primary treatment for locally advanced adenocarcinoma of the esophagogastric junction remains surgery combined with neoadjuvant chemo- or chemoradiotherapy (NT). A prediction of response to NT would be valuable, as insufficient response following NT may reflect therapy resistance leading to disease progression, unnecessary delay of surgery and risk of unresectability. Determining insufficient response to NT could lead to change of therapy and reduce possible chemo(radio)therapy toxicity. Positron Emission Tomography (PET)/Magnetic Resonance Imaging (MRI) is a new modality that has showed promising results for various clinical indications. Currently, evaluation of neoadjuvant therapy (NT) among patients with adenocarcinoma of the esophagogastric junction has primary been reserved for PET/computed tomography (CT). The aim of this study was to investigate if simultaneous PET/MRI is a feasible method to evaluate early tumor response to predict resectability in patients with AEG during NT. We also examined the association between histopathological response and changes on PET/MRI during NT. Methods Patients with untreated adenocarcinoma of the esophagogastric junction (Siewert's I/II) and fit for NT with no contraindications for PET/MRI were considered eligible. A baseline scan was performed prior to NT induction and an evaluation scan 3 weeks later. For histopathological response evaluation the Mandard tumor regression grade score was applied. Response on PET/MRI was evaluated with Response Evaluation Criteria in Solid Tumors (RECIST 1.1), and change in ADC and SUVmax values. Results Twenty-eight patients were enrolled, and 22 completed both scans and proceeded to our final analyses. 17 patients were found resectable vs. five not resectable. PET/MRI response evaluation is a feasible method to predict resectability in patients with adenocarcinoma of the esophagogastric junction with sensitivity 94%, specificity 80%, and AUC = 0.95. However, no association with histopathological response (tumor regression grade) was found nor was RECIST correlated with resectability. Conclusion Our work has identified response evaluation with PET/MRI as a feasible method to predict resectability in patients with adenocarcinoma of the esophagogastric junction, however, larger studies are warranted to justify the use of this modality for this indication. Disclosure All authors have declared no conflicts of interest.