Optimizing the methodology for calculating the 4DCT derived internal target volume in stereotactic radiotherapy for Non-Small Cell Lung Cancer (NSCLC)

Abstract

Author(s): Arun Balakrishnan, Ramesh Babu

This study aimed to investigate efficient methods for determining the Internal Target Volume (ITV) using Four-Dimensional Computed Tomography (4DCT) images in Stereotactic Body Radiotherapy (SBRT) for patients with early-stage Non-Small Cell Lung Cancer (NSCLC). The study involved 55 patients who underwent SBRT for stage I NSCLC, with their 4D CT images analyzed to determine the ITVs. The Matching Index (MI) for ITV4Phases and ITV2Phases was calculated as the ratio of these volumes to ITV10Phases. Significant differences were observed among the various ITVs, with distinct orders for ITV10Phases, ITV4Phases, and ITV2Phases. Notably, the MI for ITV4Phases was significantly higher than that for ITV2Phases. Additionally, there was an inverse relationship between the MI of ITV4Phases and the Total Motion Index (TMI) (r=0.0067, p=0.5507). In a subgroup with low TMI, ITV4Phases did not show a significant difference from ITV10Phases (p=0.8003), and its MI was significantly higher than that of ITV2Phases.Therefore, ITV4Phases emerges as a potentially efficient alternative to the optimal ITV10Phases in SBRT for early-stage NSCLC, especially in cases with reduced tumor motion.

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