Materials and methods: We investigated the utility of metabolic tumor width parameters in predicting response to chemoradiotherapy and in predicting disease-free survival in patients with esophageal cancer. Furthermore, we evaluated the possible confounding effect of therapy-induced esophagitis on the evaluation of treatment response. Forty-nine patients with squamous cell carcinoma, who had undergone positron emission tomography/computed tomography (PET/CT) exams before and after neoadjuvant chemoradiotherapy, were included in the study. In the slice with the maximum 2-deoxy-2-[F-18]fluoro-D: -glucose (FDG) uptake of the tumor, the following metabolic tumor width parameters were measured: Area of the tumor, maximum diameter of the tumor, maximum and mean standardized uptake value (SUV). Furthermore, the "diameter-SUV index" was calculated by multiplying the tumor diameter by the mean SUV.
Results: The decrease of the metabolic tumor diameter between pre- and post-treatment PET/CT scans was the single best predictor of treatment response and tumor-free survival. However, the accuracy of predicting response and survival was even higher when using the decrease of the "diameter-SUV index" as the metabolic criterion for treatment response. A decrease by more than 55% of the diameter-SUV index identified pathologic responders (n = 22) with a sensitivity of 91% and a specificity of 93%. Radiation esophagitis was found to have a significant impact on the assessment of treatment response when evaluating therapy response based on the maximum SUV, whereas no confounding effect of radiation esophagitis was seen when evaluating therapy response based on the tumor diameter or the diameter-SUV index.
Conclusion: The present study shows that tumor width parameters, especially the tumor diameter or the combination of diameter and SUV in the "diameter-SUV index", are valuable for predicting tumor-free survival and treatment response independent from the presence of radiation esophagitis.