Background There is no consensus strategy for treatment of T4 esophageal cancer, and because of this, a better evaluation of treatment response is crucial to establish personalized therapies. This study aimed to establish a useful system for evaluating treatment response in T4 esophageal cancer. Methods This study included 130 patients with cT4 esophageal cancer without distant metastasis who underwent 18F-fluorodeoxyglucose-positron emission tomography before and after a series of induction treatments comprising chemoradiation or chemotherapy. We evaluated the maximal standardized uptake value and treatment response. Results The mean ± standard deviation of standardized uptake value in the primary tumor before and after induction treatments were 13.8 ± 4.4 and 5.4 ± 4.1, respectively, and the mean standardized uptake value decrease was 58.4%. The most significant difference in survival between positron emission tomography-primary tumor responders and nonresponders was at a decrease of 60% standardized uptake value, based on every 10% stepwise cutoff analysis (2-year cause-specific survival: 60.2 vs 23.5%; hazard ratio = 2.705; P <.0001). With this cutoff value, the resectability (P =.0307), pathologic response (P =.0004), and pT stage (P <.0001) were associated with positron emission tomography-primary tumor response. Univariate analysis of 2-year cause-specific survival indicated a correlation between cause-specific survival and clinical stages according to TNM classification, esophageal perforation, positron emission tomography-primary tumor response, lymph node status evaluated by positron emission tomography before and after induction treatments, and operative resection. Multivariate analysis further identified positron emission tomography-primary tumor response (hazard ratio = 2.354; P =.0107), lymph node status evaluated by positron emission tomography after induction treatments (hazard ratio = 1.966; P =.0089), and operative resection (hazard ratio = 2.012; P =.0245) as independent prognostic predictors. Conclusion Positron emission tomography evaluation of the response of primary and metastatic lesions to induction treatments is important to formulate treatment strategies for cT4 esophageal cancer.
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