Predicting Radiation Esophagitis using 18F-FAPI-04 PET/CT in Patients with LA-ESCC Treated with Concurrent Chemoradiotherapy

Abstract Purpose: This prospective study examined whether 18 F-FAPI-04 PET/CT can predict the development and severity of radiation esophagitis (RE) in patients with locally advanced esophageal squamous cell carcinoma (LA-ESCC) treated with concurrent chemoradiotherapy. Methods: From June 2021 to March 2022, images were prospectively collected from LA-ESCC patients who underwent 18 F-FAPI-04 PET/CT examinations before and during radiotherapy. The development of RE was evaluated weekly according to Radiation Therapy Oncology Group criterion. The target-to-background ratio in blood (TBR blood ) was analyzed at each time point and correlated with the onset and severity of RE. Factors that predicted RE were identified by multivariate logistic analyses. Results: Thirty patients (median age, 66.5 years [interquartile range: 56–71 years]; 22 men) were evaluated. Significantly higher TBR blood (during radiotherapy, mean: 3.06 vs 7.11, P = 0.003) and change in TBR blood compared with pre-RT (ΔTBR blood , mean: 0.67 vs 4.81, P = 0.002) were observed in patients with RE than patients without RE. Those with grade 3 RE had a significantly higher TBR blood (during radiotherapy, mean: 4.55 vs 9.66, P = 0.003) and ΔTBR blood (mean: 2.16 vs 7.50, P = 0.003) compared with those with RE < grade 3. Receiver operating characteristic curve analysis identified TBR blood (during radiotherapy, AUC = 0.902; AUC = 0.912) and ΔTBR blood (AUC = 0.911; AUC = 0.922) as significant predictors of the development of RE and specifically grade 3 RE. On multivariate analysis, ΔTBR blood was identified as a significant predictor of both RE ( P = 0.021) and grade 3 RE ( P = 0.038). Conclusion: The ΔTBR blood on 18 F-FAPI-04 PET/CT may be effective at identifying patients at risk for the development of RE, especially grade 3 RE.