486 utility of 18f-fdg/pet for predicting histopathological response to neoadjuvant induction chemotherapy and chemoradiotherapy for esophageal and junctional carcinoma

Abstract Neoadjuvant treatment followed by esophagectomy is the standard therapy for patients with resectable esophageal cancer. Data have demonstrated that patients with pathologic complete response (pCR) have better survival. Several studies have been exploring whether 18F-FDG/PET performed during neoadjuvant treatment can predict a pCR, but the results are conflicting. The aim of this study was to assess the role of 18F-FDG PET/CT for predicting the histopathological response to neoadjuvant induction chemotherapy (IC) and chemoradiotherapy (CR). Methods Patients with proven squamous cell or adenocarcinoma of the esophagus or GEJ were enrolled in this prospective study. Patients received two cycles of IC with carboplatin and paclitaxel followed by concurrent CR and then esophagectomy. Metabolic response was evaluated according to PERSIST criteria by 18F-FDG PET/CT performed at baseline, at day 14 of chemotherapy and four to eight weeks after the completion of CR. Tumoral pretreatment, induction and posttreatment FDG-standardized uptake value normalized to lean body mass SULmean and percentage change were assessed. These parameters were correlated with the pathologic response using the Mandard tumor regression grade (TRG) scale. Results Thirty patients finished the IC plus CR and 16 had esophagectomy. The median age was 57 years, 75% were male and 56% had adenocarcinoma. The mean of SULmean prior to treatment, after one cycle of IC and after CR were respectively 6.12, 4.67 and 1.52. After one cycle of IC, one patient had metabolic progression, eight remained stable and seven had partial metabolic response. All metabolic responders had good histopathological response (Mandard 1 or 2). After CR, five patients had complete metabolic response (CMR). However, three of them had poor histopathological response (Mandard >2). Conclusion Our initial results suggests that the early PERSIST-based metabolic response evaluation appears useful to predict a good histopathological response. Thus, an interim 18FFDG PET/CT may help to identify good responders during the neoadjuvant treatment. However, the late metabolic response evaluation after CR had a poor pathologic correlation. In this way, a CMR after CR should not be assumed to be synonymous of complete pathologic response.