Intrathoracic Anatomical Changes During Stereotactic Lung Radiation Therapy: Implications for Daily IGRT

Abstract

Purpose/Objective(s)To determine the intra-thoracic anatomical changes (ITACs) during stereotactic lung radiation therapy (SBRT) and evaluated their implications of this changes on the daily image guided radiation therapy (IGRT).Materials/Methods23 patients with primary lung carcinomas or lung metastasis treated between 2012 and 2015 in our center with SBRT from 3 to 8 fractions (50-60 Gy) were retrospective analyzed. 138 CBCT were examined to define the ITACs during the course of the treatment. The patients were initially positioned in customized immobilization cradles and then aligned with stereotactic X ray and CBCT. On a second step, image guided radiation therapy (IGRT) was evaluated in order to compare the differences between soft tissue target registration and bony anatomy matching for each translational dimension in 83 daily cone beam CT (CBCT).ResultsIn 10 patients (43%) 13 ITAC’S were identified. Types of observed ITACs were tumor regression (23%), changes in atelectasis (38%), tumor progression (30%), and infiltrative changes (0.1%). Pleural effusion was not found. The difference in the couch shift obtained from the bone (stereotactic X ray) and soft tissue registration (CBCT) of 83 images was 0.03 mm for vertical, 0.03 mm for longitudinal, 0 mm for lateral axis.ConclusionITACs during SBRT are less frequent than those reported during conventionally fractionated radiation therapy. The impact of these changes perhaps is clinically irrelevant for the positioning with soft tissue registration. A larger sample is needed to validate these data. Purpose/Objective(s)To determine the intra-thoracic anatomical changes (ITACs) during stereotactic lung radiation therapy (SBRT) and evaluated their implications of this changes on the daily image guided radiation therapy (IGRT). To determine the intra-thoracic anatomical changes (ITACs) during stereotactic lung radiation therapy (SBRT) and evaluated their implications of this changes on the daily image guided radiation therapy (IGRT). Materials/Methods23 patients with primary lung carcinomas or lung metastasis treated between 2012 and 2015 in our center with SBRT from 3 to 8 fractions (50-60 Gy) were retrospective analyzed. 138 CBCT were examined to define the ITACs during the course of the treatment. The patients were initially positioned in customized immobilization cradles and then aligned with stereotactic X ray and CBCT. On a second step, image guided radiation therapy (IGRT) was evaluated in order to compare the differences between soft tissue target registration and bony anatomy matching for each translational dimension in 83 daily cone beam CT (CBCT). 23 patients with primary lung carcinomas or lung metastasis treated between 2012 and 2015 in our center with SBRT from 3 to 8 fractions (50-60 Gy) were retrospective analyzed. 138 CBCT were examined to define the ITACs during the course of the treatment. The patients were initially positioned in customized immobilization cradles and then aligned with stereotactic X ray and CBCT. On a second step, image guided radiation therapy (IGRT) was evaluated in order to compare the differences between soft tissue target registration and bony anatomy matching for each translational dimension in 83 daily cone beam CT (CBCT). ResultsIn 10 patients (43%) 13 ITAC’S were identified. Types of observed ITACs were tumor regression (23%), changes in atelectasis (38%), tumor progression (30%), and infiltrative changes (0.1%). Pleural effusion was not found. The difference in the couch shift obtained from the bone (stereotactic X ray) and soft tissue registration (CBCT) of 83 images was 0.03 mm for vertical, 0.03 mm for longitudinal, 0 mm for lateral axis. In 10 patients (43%) 13 ITAC’S were identified. Types of observed ITACs were tumor regression (23%), changes in atelectasis (38%), tumor progression (30%), and infiltrative changes (0.1%). Pleural effusion was not found. The difference in the couch shift obtained from the bone (stereotactic X ray) and soft tissue registration (CBCT) of 83 images was 0.03 mm for vertical, 0.03 mm for longitudinal, 0 mm for lateral axis. ConclusionITACs during SBRT are less frequent than those reported during conventionally fractionated radiation therapy. The impact of these changes perhaps is clinically irrelevant for the positioning with soft tissue registration. A larger sample is needed to validate these data. ITACs during SBRT are less frequent than those reported during conventionally fractionated radiation therapy. The impact of these changes perhaps is clinically irrelevant for the positioning with soft tissue registration. A larger sample is needed to validate these data.