Detecting Interval Metastases and Response Assessment Using 18F-FDG PET/CT After Neoadjuvant Chemoradiotherapy for Esophageal Cancer

Abstract

The aim of this study is to evaluate the potential of FDG PET/CT for the detection of interval distant metastases after neoadjuvant chemoradiotherapy (CRT) and the prediction of the pathologic response to CRT in esophageal cancer patients. In this retrospective study, all esophageal cancer patients for whom CRT followed by surgery was planned between January 2008 and April 2013 and in whom an FDG PET/CT was performed before and after CRT were included. For the response analyses, both FDG PET/CT scans had to be made on a similar scanner. Metabolic response of the primary tumor was assessed using the SUVmax, metabolic tumor volume (MTV), and total lesion glycolysis (TLG). These parameters were correlated with the pathologic response using the tumor regression grade (TRG) scale according to Mandard et al (Cancer. 1994;73:2680-2686). In 6 (8%) of 76 consecutively treated patients, new distant metastases were detected on FDG PET/CT after neoadjuvant CRT; these patients therefore did not undergo operation. Forty-eight (63%) of 76 patients were eligible for response analysis. The relative change in SUVmax, MTV, and TLG was significantly different between patients with a major (TRG, 1-2) and a minor response (TRG, 3-5) but not between patients with and without a pathologic complete response. The area under the curve of the receiver operating characteristic for predicting a major response was 0.70 (95% confidence interval, 0.65-0.92) for a relative decrease in SUVmax, compared with 0.73 (95% confidence interval, 0.58-0.88) both for MTV and TLG. A relative decrease in SUVmax of 60% or more had the highest positive predictive value (75%). Futile surgery was prevented in 8% of our esophageal cancer patients because interval metastases were detected on an FDG PET/CT after neoadjuvant CRT. The accuracy for predicting a complete or major pathologic response was limited and does not support the use of FDG PET/CT for refraining from surgical treatment.