Early Experiences of Deep Inspiration Breath Hold Technique in Stereotactic Body Radiotherapy for Localized Lung Tumor

Abstract

Organ motion management in stereotactic body radiotherapy (SBRT) for localized lung tumor is key for a successful treatment delivery. We would like to describe our limited clinical experiences of deep inspiration breath hold (DIBH) technique in stereotactic body radiotherapy for localized lung tumor and compare the dosimetric results with free breathing (FB) technique. Five patients with Tumor Staging T1 – T2 N0 M0 (Size < 5.0 cm) with peripheral lesion were treated with DIBH-SBRT were included in this study. All the five patients under went CT simulation using DIBH and 4D-CT for FB techniques. Plans were created using two to three coplanar modulated partial arcs using 10MV flattening filter free (FFF) bream with a dose rate of 2400 MU/min in both FB and DIBH CT data sets using True Beam Linear accelerator. Same dose constraints for the target and the critical structures for a particular patient were used during the plan optimization process in DIBH and FB datasets. All the patients received 50 Gy in 5 fractions (BED10 100 Gy10) for all the patients using DIBH CT dataset on the other hand FB data set plans were only used for dosimetric comparisons. Daily gated DIBH cone-beam CT were performed for all the patients during treatment delivery. For standardization, all the plans were normalized at target mean of the planning target volume (PTV). Doses to the critical structures and targets were recorded from the dose volume histogram for evaluation. The overall survival (OS) and local control (LC) and toxicity assessment were documented during the follow-up. In spite of our small sample size, there is a strong evidence that DIBH-SBRT plans were far superior to the FB-SBRT plans. The mean age of all the patients is 65.2 years (range 55 to 78 years) with a mean follow-up of 24.2 months (range 10 to 32 months). Out of five patients, four patients are still alive with complete remission of disease and one patient died after 10 months due to septicemia during blood transfusion. No grade 3 acute and late toxicity were documented during treatment and follow-up. The mean right and left lung volumes were inflated by 1.55 and 1.60 times in DIBH scans compared to the FB scans. The mean internal target volume (ITV) increased in the FB datasets by 1.45 times compared to the DIBH data sets. The mean dose followed by standard deviation (x̄ ± sx̄) of ipsilateral lung for DIBH-SBRT and FB-SBRT plans were 7.48 ± 3.57 (Gy) and 10.23 ± 4.58 (Gy) respectively, with a mean reduction of 36.84% in DIBH-SBRT plans. Ipsilateral lung was reduced to 36.84% in DIBH plans compared to FB plans. Significant dose reduction in ipsilateral lung due to the lung inflation and target volume reduction due to motion restriction in DIBH-SBRT plans were observed compare to FB-SBRT. DIBH-SBRT plans demonstrate superior dose reduction to the normal tissues and other critical structures. DIBH-SBRT provides us simpler and safer organ motion management in the treatment of localized lung tumor.