Significance of mid-radiotherapy 18F-fluorodeoxyglucose positron emission tomography/computed tomography in esophageal cancer

•Tumor metabolism changes in mid-radiotherapy is useful predictor for treatment response and recurrent in patients with esophageal cancer.•The early response evaluation obtained from mid-radiotherapy 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is significantly associated with prognosis of patients.•Maximum standardized uptake value (SUVmax) is significantly parameter associated with both locoregional recurrence and distant metastasis. Metabolic parameters evaluated by 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) are known as prognostic markers in various cancers. We aimed to validate the predictive value of mid-radiotherapy (RT) FDG PET/CT parameters in esophageal cancer. Eighty-three patients treated with RT with or without chemotherapy between 2015 and 2020 were included. PET parameters including metabolic tumor volume (MTV), total lesion glycolysis, and mean (SUVmean) and maximum standardized uptake value (SUVmax) were analyzed. Locoregional recurrence-free rate (LRFR) and distant metastasis-free rate (DMFR) were analyzed. The median follow-up period was 10.5 months. Mid-RT SUVmax was significantly associated with LRFR (HR 1.07, p = 0.009) and DMFR (HR 1.13, p = 0.047) while mid-RT MTV was associated with DMFR (HR 1.06, p = 0.007). Treatment response after RT was associated with overall survival (HR, 1.52, p = 0.025). Further, treatment response was significantly associated with mid-RT SUVmax. The optimal cutoff value for mid-RT SUVmax in predicting LRFR and DMFR was 11 while cutoff value for mid-RT MTV was 15. The patients with mid-RT SUVmax ≤ 11 showed superior LRFR and DMFR compared to SUVmax > 11 (1-year LRFR; 73.4% vs. 48.4%, p = 0.028, 1-year DMFR; 74.6% vs. 40.7%, p = 0.007). The 1-year DMFR was significantly different between patients with mid-RT MTV ≤ 15 and >15 (1-year DMFR; 78.2% vs. 31.9%, p = 0.002). Tumor metabolism changes during RT can be a useful predictive tool for treatment response and recurrence in patients with esophageal cancer. Clinicians may consider early response evaluation with PET during RT for predicting prognosis information about prognosis.