Dosimetric and Volumetric Analysis in Endobronchial Brachytherapy in Lung Carcinoma: A Cross-sectional Study

Abstract

Introduction: High Dose Rate (HDR) brachytherapy plays an important role in the treatment of lung carcinoma. The treatment of lung carcinoma with Endobronchial Brachytherapy Treatment (EBBT) is delivered with three fractions and the effect of EBBT on the Target Volume (TV) after delivering the three fractions in the lung carcinoma needs to be assessed. The TV is covered with the prescribed dose and Organs At Risk (OARs) doses are evaluated. Aim: To assess the doses to OAR nearby the tumour and analyse the effect of the TV, tumour location, and site on the doses to OARs in EBBT in lung carcinoma. Materials and Methods: A cross-sectional study was conducted in the Department of Radiation Oncology, Cancer Research Institute, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University Dehradun, Uttarakhand, India, from January 2018 to December 2020. Thirty patients with lung carcinoma were included in dosimetric and volumetric assessments. A flexible lumencare catheter was inserted into the bronchial lesion. Computed Tomography (CT) scan was acquired and exported to Treatment Planning System (TPS) through Digital Imaging and Communications in Medicine (DICOM) networking system. An optimised treatment plan was generated. The TV and OARs were delineated on the CT scan of the patient. A total of three EBBT sessions were given with a 7 Gy dose per fraction and prescribed the dose at 1.0 cm from the center of the catheter. Doses to OARs and the effects of TV on doses to OARs were evaluated with the help of “Dose Volume Histogram (DVH) tool” in the TPS. Thirty patients, with varying TV and site, were grouped as left lung and right lung tumour lesions and also grouped as TV <22 cc and TV >22 cc for the analysis purpose in this study. The data was entered in Microsoft Office Excel 2007 and analysed in Statistical Package for the Social Sciences (SPSS) version 22.0 statistical analysis software (IBM Corp., Armonk, N.Y., USA) tool. Results: The mean doses to OARs in 1st, 2nd and 3rd EBBT sessions were within their tolerance limit. The mean dose difference between left and right lung tumour site were analysed and found mainly the mean dose to oesophagus and maximum dose to oesophagus, contralateral lung, left coronary artery and descending aorta were significantly higher in left lung compared to right lung with p-value 0.015, 0.027, 0.001, 0.007 and 0.001, respectively. The maximum dose to the contralateral lung and spinal cord were significantly higher in middle-lower bronchial lesion with p-value 0.024 and 0.023, respectively. The mean dose difference between left and right lung tumour volume for TV <22 cc and TV>22 cc was analysed and found mainly for the group TV>22 cc the mean dose to oesophagus and maximum dose to oesophagus, Heart, contralateral lung, left coronary artery and descending aorta were significantly higher in the left lung compared to right lung with p-value 0.002, 0.008, 0.027, 0.003, 0.006 and 0.001, respectively whereas in the TV<22 cc group only the contralateral lung max dose was significantly higher in left lung compared to right lung with p-value 0.046. Conclusion: The OARs doses were increased significantly in left lung compared to right lung carcinoma. The TV was large in the middle-lower bronchial region, therefore, the doses were found higher, and TV in the lower bronchial region is less so the dose was less.