Evaluation of early response to concomitant chemoradiotherapy by interim 18F-FDG PET/CT imaging in patients with locally advanced oesophageal carcinomas

The best way to assess the response to chemoradiotherapy of locally advanced oesophageal carcinomas is not known. We used 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT to evaluate the metabolic response during chemoradiotherapy and tried to correlate this response to survival. Patients with biopsy-proven oesophageal carcinoma underwent FDG PET/CT with evaluation of the standardized uptake value (SUV) before any treatment (SUV1) and during chemoradiotherapy after two cycles of 5-fluorouracil (FU)/cisplatin and 20 Gy (SUV2). Metabolic response was defined as 1-(SUV2/SUV1). Surgery was discussed after 40 Gy and three cycles of chemotherapy. Results of interim PET were not considered for the therapeutic decision. Among 72 patients who underwent a first FDG PET/CT before any treatment, 59 (82 %) could receive the second FDG PET/CT examination. Median survival was 22.2 months with 1-year and 2-year survivals of 70 and 46 %, respectively. Nineteen patients (32 %) underwent surgery. Mean SUV1 and SUV2 were 12.3 ± 6.2 and 6 ± 4.1, respectively (p < 0.001). Using a cut-off for metabolic response of 50 %, sensitivity and specificity for survival were 0.7 and 0.58. The 2-year overall survival of good responders was 62 % as compared to 27 % for poor metabolic responders. A multivariate analysis was performed, including T and N stages, surgery, histology and metabolic response: only metabolic response was significantly (p = 0.009) associated with 2-year survival. Early evaluation of metabolic response had a great prognostic value and could help identify good responders to chemoradiotherapy. (orig.)