Dose Comparisons For Radiotherapy Plans Between Simultaneously Integrated Boost Intensity-modulated Radiotherapy And Sequential Boost Intensity-Modulated Radiotherapy In Middle Thoracic Esophageal Carcinoma

BackgroundEsophageal cancer is a worldwide epidemic disease,ranking the seventh most common malignant tumor,the sixth leading cause of cancer-related deaths in the world and the fifth leading cause of cancer-related deaths in the developing countries.The incidence of esophageal cancer showed notable geographic variability.The incidence in developing countries is higher than the developed countries and in rural areas is higher than in cities.The morbidity and mortality in males are higher than females.In the western countries esophageal cancer usually occurs in the lower 1/3 of the esophagus and involving the esophagogastric junction,while in China,esophageal cancer often localizes in the mid-thoracic esophagus,followed by the lower thoracic esophagus.The dominant histological types of esophageal cancer consist of squamous cell carcinoma and adenocarcinoma.These two subtypes vary in terms of risk factors and high-prevalence areas.Among them,the high-incidence regions of esophageal squamous cell carcinoma predominantly include Eastern Europe and Asia,whereas adenocarcinoma is the most common subtype in Western Europe and North America.Smoking and alcohol consumption are main risk factors for esophageal squamous cell carcinoma while the causes of esophageal adenocarcinoma are closely related to smoking,obesity and Barrett's esophagus.The symptoms of patients with different histological types are similar,including progressive dysphagia,choke when drinking,poor appetite,chest pain,and weight loss.Local uncontrolled or recurrence is the major treatment failure pattern in patients with esophageal cancer.There was almost no distinction in the treatment between the two histological types.At present,surgery is widely considered as the principal treatment for resectable esophageal cancer as before.For unresectable patients with locally advanced or metastatic esophageal cancer,combined modality treatment based on radiotherapy and chemotherapy is the integral paradigm.Radiotherapy plays an irreplaceable role in its treatment.The purpose of this study is to compare the difference between the two radiotherapy plans of simultaneous integrated boost intensity-modulated radiotherapy(SIB-IMRT)and sequential boost intensity-modulated radiotherapy(SB-IMRT)in terms of dosimetry,to provide a reference for the selection of clinical treatment plan.ObjectiveTo evaluate the pros and cons of SIB-IMRT and SB-IMRT in dosimetric parameters for patients with middle thoracic esophageal cancer.Material and methodsThe images of CT positioning of 20 patients with mid-thoracic esophageal carcinoma who accepted radiotherapy in the first therapy stage between January 2017 and March 2019 in the affiliated cancer hospital of Zhengzhou University were obtained.Treatment plans for the 20 patients were developed using two modalities including SIB-IMRT and SB-IMRT.SIB-IMRT plans were designed to deliver 50.40 Gy in 28 fractions to PTV while simultaneously delivering 59.92 Gy in 28 fractions to PGTV;In contrast,SB-IMRT plans delivered 50 Gy in 25 fractions to PTV in the first plan,and 10 Gy in 5 fractions to PGTV in the second plan.The analyses of Homogeneity Index(HI),Conformity Index(CI),Target Coverage(TC)and dose distribution were carried out for each plan.ResultsThe CI of SIB-IMRT group was superior than SB-IMRT group obviously(P=0.039).The HI of the former was higher than the latter,but there was no significant difference between the two plans(P=0.394).The comparison of the SIB-IMRT and SB-IMRT showed no significant difference in TC(P=0.069).The maximum dose of PGTV and PTV in SIB-IMRT group were higher than those in SB-IMRT group(P<0.001,P=0.007).V5,V10,V20,V30,and mean lung dose of Lung,V20,V50,and mean dose of heart in SIB-IMRT group were lower than SB-IMRT group(P<0.001,P<0.001,P=0.001,P<0.001,P<0.001,P=0.005,P<0.001,P<0.001,respectively).SB-IMRT group showed inferior in the maximum dose and mean dose of spinal cord than SIB-IMRT group,but the differences were not statistically significant(P=0.698,P=0.805).ConclusionIn contrast to SB-IMRT,SIB-IMRT offered advantages in terms of dose distribution and reducing dose of organs at risk,particularly in critical cardiopulmonary organs.