FDG PET findings are predictive of histopathological response after neoadjuvant therapy for esophageal cancer

1724 Objectives: Neoadjuvant therapy (NAT) with combined radiation treatment and chemotherapy is being employed prior to esophagectomy for esophageal cancer. Complete histopathological response after NAT has been known to correlate with favorable long term prognosis. The aim of this study was to determine the ability of FDG PET imaging in predicting histopathological results after NAT in patients with esophageal cancer. Methods: FDG PET images of 38 patients (males 30 and females 8) with esophageal cancer were reviewed. PET image before and after NAT were compared for residual disease activity. Based on PET findings Patients were divided into 3 groups - those with complete resolution, partial resolution and no resolution of the baseline FDG activity in the primary tumor. The PET results were then compared with the histopathological examination after esophagectomy for the presence or absence of residual tumor in the resected specimen. Results: Complete resolution of the primary tumor FDG uptake (group 1) was seen in 23 patients, partial resolution (group 2) in 7 patients and no resolution (group 3) in 8 patients. Eighteen patients in group1 (79 %) had no residual tumor on the esophagectomy. Of the 5 patients in group 1 who had residual tumor two had local nodal disease and 3 had poorly differentiated adenocarcinoma. Three patients in group 2 had no residual tumor and 4 patients had residual tumor. One patient in group 3 did not have surgery. All of the remaining 6 patients (100%) in group 3 had residual tumor. Conclusions: Findings of our study show that complete resolution of the primary tumor FDG uptake after NAT is strongly predictive of histopathological response after esophagectomy in patients with esophageal cancer. However tumors which become undifferentiated despite NAT may also show no FDG uptake. Lack of resolution of the FDG uptake after NAT is highly suggestive of the persistence of residual tumor which has prognostic implications.