A new method to characterize target location in lung cancer patients treated with stereotactic body radiation therapy

Abstract

Purpose: Stereotactic body radiation therapy is an emerging technique in the treatment of peripheral lung tumors. However, due to early reports of increased toxicity, the treatment of central lung lesions with hypo-fractionated high-dose regimen remains controversial. Thus far, lung lesions have been defined as either central or peripheral depending solely on their nearest distance from the major airways. The goal of this study is to develop a quantitative method to categorize the location of lung lesions mapped in three-dimensional space. Furthermore, a set of parameters are proposed for assessing risk factors based on target locations. Methods and Materials: A MATLAB program was developed to quantify the distance between the tumor and the airways, and to calculate the percentage of the target volume lying within a given distance from the main bronchial tree. The program was tested on 20 patients with centrally located lung lesions treated with CyberKnife. A dosimetric analysis was performed to investigate the relationship between dose delivered to the critical structures and target location. Results: The absolute target volume located within a distance of 20 mm from the airways was used to quantify the tumor proximity to the bronchial tree. A strong correlation was found between this parameter and the dose delivered to the critical organs, showing that a detailed knowledge of target location can be used to assess the risk of toxicity during the planning stage. Conclusions: We have developed a tool to quantify the lesion proximity to the bronchial tree. We expect that risk-adapted strategies, accounting for the exact geometric relationship between the tumor and the airways, may improve the management of centrally located lung lesions. © 2012 Springer-Verlag.